Is this homebrew mechanoid race balanced?

Question

Is the following homebrew race balanced?

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Mechanoid

Ability score increase: +2 to Intelligence and +2 to Wisdom

Age: Mechanoids live an average of 40 years, but can live much longer.

Size: Medium

Speed: Your base walking speed is 30 feet. If you swim for more than 5 minutes, you are paralyzed. You recover from this paralysis after spending 30 minutes out of the water.

Condition immunities: You cannot be charmed or poisoned.

Damage immunities: You are immune to psychic, poison, radiant, and necrotic damage.

Living construct: You do not need to eat, drink, or breathe, and cannot be infected with diseases. Instead of sleeping, you only need to rest for 4 hours, during which you are alert and can speak. However, you are paralyzed while resting until the 4 hours are completed. In addition, you have disadvantage on saves against being frightened.

Damage vulnerability: You are vulnerable to acid, lightning, piercing, and slashing damage.

Alert: While you are conscious, you have a +2 bonus to Wisdom (Perception) checks and initiative rolls.

Innate spellcasting: You know the shocking grasp cantrip, and can cast detect magic once per day.
At level 3, you can cast legend lore once per day.
At level 7, you learn the fire bolt cantrip.
At level 10, you can cast magic missile twice per day as a 1st-level spell.
At level 20, you can cast etherealness once per day.

Answer 1

No, it is not balanced, and probably not even playable

I'll go over the traits one by one.

Ability score increase: +2 to Intelligence and +2 to Wisdom

Pretty powerful, since most races get +2/+1, but nothing breaking if the other abilities are okay.

Speed: Your base walking speed is 30 feet. If you swim for more than 5 minutes, you are paralyzed. You recover from this paralysis after spending 30 minutes out of the water.

This basically says "cannot participate in underwater adventures, and needs to wait them out." That's either a strong restriction on the DM to not include too much water, or it means the player will be sitting out the entire part of the adventure that involves travelling under/through water.

Condition immunities: You cannot be charmed or poisoned.

This is very powerful. Poisoned is a very common and annoying ability, and Charmed is not very common but usually really debilitating. Note that both the Elf and the Dwarf get Advantage to one of these two; flat out being able to ignore both is probably too much.

Damage immunities: You are immune to psychic, poison, radiant, and necrotic damage.

No single race gets even 1 immunity to damage, and you give them 4. Including two pretty common ones. Both Poison immunity or Necrotic immunity makes a considerable number of monsters utterly non-threatening. This is definitely too much.

*There is an exception: Yuan-Ti get immunity to poison as well, but they are monstrous adventurers and the chapter they appear in already calls out that they can be unbalanced and should be used with care.

Living construct: You do not need to eat, drink, or breathe, and cannot be infected with diseases. Instead of sleeping, you only need to rest for 4 hours, during which you are alert and can speak. However, you are paralyzed while resting until the 4 hours are completed. In addition, you have disadvantage on saves against being frightened.

As mentioned in the comments, this is a death sentence. Being unable to wake up means that nightly ambushes, which are already dangerous, will have to be handled without you, and your party members need to protect you from taking random critical hits. This ability is going to be utterly un-fun for the player, as again they'll have to be sitting out entire encounters.

Also, what does having disadvantage on saves against being frightened have to do with being a Living Construct?

Damage vulnerability: You are vulnerable to acid, lightning, piercing, and slashing damage.

This one pretty much makes the race unplayable entirely. No other race has vulnerabilities, and you have them against 2 of the physical damage types and 2 of the magical ones. You are not going to survive to level 2, as a single Goblin arrow will likely kill you outright. Unless you play something with a high HD, except you will not be able to fight in close combat ever if you take double damage from just about every monster in the book.

Innate spellcasting: You know the shocking grasp cantrip, and can cast detect magic once per day.

This is fine. Interesting that you let them use a racial cantrip that will likely kill another member of their race because they are vulnerable to the damage it does.

At level 3, you can cast legend lore once per day.

You are giving your race access to a 5th level spell 6 levels earlier than a spellcaster would. This would be utterly overpowered except for the fact that you picked a spell with a 250gp consumed material component and 200gp of non-consumed components, so you probably won't be able to afford casting it anyway, making this feature almost meaningless when you get it.

At level 7, you learn the fire bolt cantrip.

This is okay, although I don't know why you'd need another cantrip. This race can essentially only play ranged spell-casters, so you'll have plenty of cantrips anyway.

At level 10, you can cast magic missile twice per day as a 1st-level spell.

At level 10, this is probably meaningless. (Besides, you won't live that long). Being able to cast 2 level 1 spells is nice, but the race doesn't really need this feature.

At level 20, you can cast etherealness once per day.

No other race gets a 7th level racial spell, or a new ability at this high a level. I'm not sure how it fits thematically with anything, or what the use of this is going to be. The main purpose seems to be sitting out even more encounters by travelling to the Border Ethereal so you can't be hurt.

Answer 2

This is hugely unbalanced

The only Player's Handbook race that offers a +2 bonus to two separate ability scores is Mountain Dwarf, so let's compare to the Mountain Dwarf.

Speed

A mechanoid's walking speed is strictly better at 30 feet and with an either minor swimming weakness or serious (possibly game ruining) handicap depending on the adventure.

Side note: While not a balance concern per se: in a campaign where water is of such importance that you will be regularly swimming for more than 5 minutes without a break, no one will play this race. Also, in a situation where swimming is pertinent, the party will either find a different route or be needlessly punished for a decision made at the start of the game.

Condition Resitances/Immunities

Compare this to Dwarven Resilience which merely gives you advantage on saving throws against the poisoned condition. A mechanoid gets full immunity to the poisoned condition, something that shows up on the Yuan-ti Pureblood (likely the most overpowered official race to date). Then, on top of that, immunity to the charmed condition, another extremely common condition. So again, strictly better and severely overpowered.

Dwarven Combat Training and Tool Proficiency

These are largely secondary effects, and are roughly equivalent to Living Construct. I'd probably consider living construct to be slightly better (especially the portion where mechanoids needn't breathe, ironically making them better underwater than many NPCs for the 30 minutes that they can swim).

Nevertheless, all of these features are circumstantial and, thus, will just be hand-waved for my analysis.

Side note: Again, the paralysis bit is hugely penalizing and likely will lead to excessively cautious resting, rather than any meaningful weakness from the paralysis. At least until the party gets lesser restoration to mitigate the problems that arise from a mid-rest ambush. I strongly advise against designing homebrew weaknesses that will just seem like the GM is targeting the weakness specifically in circumstances where they come up.

Skills

Mountain Dwarves get a powerful bonus to a very specific use of a rarely used skill through Stonecunning. Even though Expertise is very good, the niche circumstances required to benefit from this make Stonecunning almost negligible.

In it's place, the mechanoids get a +2 bonus to two of the most useful ability checks in the game. This is leagues above the power level of the Mountain Dwarf feature.

Dwarven Armor Training

This is the last feature of the Mountain Dwarf and is not nearly as powerful as the Innate Spellcasting mechanoids get. Firstly, many classes get these proficiencies anyway, and the Innate Spellcasting feature provides more spells than any official race.

Now to contend with the Damage modifications.

First of all, immunities are extremely powerful. The number of official ways to gain immunity can be counted on one hand and at least 2 of them are legendary magic items. The vulnerabilities don't begin to compensate, even if they are on common damage types.

Additionally, with bounded accuracy and some class features, these vulnerabilities are all too easy to mitigate. Having extremely high AC or acquiring resistance from a barbarian Rage, for example, negates these weaknesses and shows just how powerful the immunities are.

Side note: Having so much modifications to damage types makes decisions about encounter difficulty much more difficult since some monsters that should be a cakewalk become lethal and some of the most powerful creatures are useless. I strongly advise against modifying more than one or two damage types as a racial feature and never with full immunity.

TL;DR

All of the features of the proposed Mechanoid are beyond the power level of the Player's Handbook races and far too powerful for standard 5th edition play. Most of the weaknesses you implement to attempt to compensate for the race's strengths are either too circumstantial, circumventable to the point of abuse, or just downright non-conducive to balanced play.

Mostly this comes down to trying to create a many strengths/many weaknesses homebrew. This is okay for monsters who are designed for a one-combat spotlight, but not for PCs or NPCs who need to take on multiple types of challenges over the course of its adventuring or villain life.