(In this case) The Player controls the ordering
Xanathar's Guide to Everything includes an (optional) rule for exactly this situation. On page 77, it contains a section entitled "Simultaneous Effects":
In rare cases, effects can happen at the same time, especially at the
start or end of a creature's turn. If two or more things happen at the
same time ...
They take damage from both fireballs
The key for me is the word "effects" from your quote:
The effects of the same spell cast multiple times...
I would argue that the damage dealt from the fireball is not an "effect" in the context of what your quote is talking about. This spell simply deals damage and has no additional "effects&...
They're supposed to be the same spell; the only reason the names are different is because of copyright/legal issues. So you shouldn't be having both of them in your game.
Trying to argue they are two different spells is trying to rules-lawyer something that was only done to appease real lawyers and suggesting this in seriousness is likely going to earn you ...
No, you must start your turn with 0 HP
Under the section titled Death Saving Throws the Basic Rules state:
Whenever you start your turn with 0 hit points, you must make a special saving throw, called a death saving throw.
Before you start your turn, how many hit points do you have? If it is more than 0, then you will not make a death saving throw, because ...
Your example is somewhat flawed. If Bob readies an action to attack Alice as soon as she's within reach, and then moves within reach, it's just a normal move/attack sequence. No Readying is necessary, in which case Alice resolves her readied attack as soon as Bob is within reach and then Bob acts.
Let's go with another example.
Alice has the best ...
For the wraith, the damage comes first then HP reduction
There is no general rule that I know of that would determine the order in which these effects would be applied in generally. However, the wording of the wraith's ability specifically tells us the order.
The wraith's life drain says:
...its hit point maximum is reduced by an amount equal to the damage ...
Comes down to when the Wizards chose to use their Portent
The main concern here is going to be Metagaming. The Diviner chooses to use their portent before the roll as shown here (emphasis mine):
You can replace any attack roll, saving throw, or ability check made by you or a creature that you can see with one of these foretelling rolls. You must choose to ...
For simultaneous saves, there is an optional rule
Generally, when one is making a saving throw you are making them one at a time in the order they occur. That is the rule that saving throws operate under normally. However, if the saves somehow end up happening at the same time with no logical way to separate them, we do have an optional rule that will help.
The creature takes damage from both spells.
Moonbeam is cast on an area, not a creature. It then causes damage to creatures within that area. The effect of said damage is instantaneous, and so the rules for overlapping spells doesn't apply.
Xanathar's Guide to Everything has guidelines for simultaneous effects; the person whose turn it is determines the order of simultaneous events
The meteor swarm spell states:
[...] A creature takes 20d6 fire damage and 20d6 bludgeoning damage on a failed save, or half as much damage on a successful one [...]
It gives no indication of these happening at ...
The SRD isn't official rules material, so this is a non-issue for official rules
The SRD isn't an official rules resource, so material from the SRD is effectively irrelevant to rules questions (except where material from an official rules resource is identical to it). In other words, if we're limiting ourselves to "official 5e rules", this question ...
This is combining the same spell multiple times.
The rule you're referencing is found in chapter 10 of the PHB, Spellcasting, in the subsection Combining Magical Effects. [emphasis mine]
The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however. Instead, ...
A creature cannot be actively affected by two instances of the same spell, this includes the warded creature; one saving throw is made
The rules on "Combining Magical Effects" state:
[...] The effects of the same spell cast multiple times don't combine, however. Instead, the most potent effect—such as the highest bonus--from those castings applies ...
Being hit and taking damage are part of the single “event” Resolve the Attack which says:
3. Resolve the attack. You make the attack roll. On a hit, you roll damage, unless the particular attack has rules that specify otherwise. Some attacks cause special effects in addition to or instead of damage.
Getting hit and taking damage are different ...
Your Interpretation is Correct
In D&D 5e specific beats general. That is:
If a specific rule contradicts a general rule, the specific rule wins.
In this case Damage Immunity: Fire is a general rule that applies to many creatures, allowing them to take no damage from fire. Fire Absorption is given in the monster's statblock and specifically describes ...
Casting Time Stop #2 whilst Time stop #1 is already in effect will cancel Time Stop #1.
So first of all, Time Stop (TS) #1 is cast. Casting TS #2 will cancel TS #1 based on its spell description:
You briefly stop the flow of time for everyone but yourself. No time passes for other creatures, while you take 1d4 + 1 turns in a row, during which you can use ...
Yes, you can cast multiple spells at the same time and have both take effect
There are no rules against this
The rules are fairly clear about what is and is not allowed with regards to when and how spells can be cast. The restrictions on spellcasting timing come down to two major rule categories:
As long as you have the action ...
Your intuition is correct. Although the described effects occur on the same turn and from the same trigger, they are two separate and unique effects that need to be adjudicated separately. This is most readily construed by virtue of Fireball's Instantaneous duration and there are an infinite number of Instantaneous durations that occur on any one ...
Dissonant Whispers happens.
With Misty Escape, the warlock "can" use their reaction to teleport away, but when failing a save against dissonant whispers the warlock "must immediately" use their reaction to flee.
In D&D specific beats general, and "must" is more specific than "can" because "must" is compulsory while "can" is optional.
So, the effect of ...
They would stack because they have no duration
The rules on stacking/combining game effects states (page 252):
[W]hen two or more game features have the same name, only the effects of one of them — the most potent one — apply while the durations of the effects overlap
I would argue that modifiers to rolls do not actually have a duration and so they ...
As it's your turn, you get to decide!
Xanathar's Guide to Everything contains an optional rule to help adjudicate this.
On page 77 (or here on DNDBeyond, if you own it there):
If two or more things happen at the same time on a character or
monster's turn, the person at the game table-whether player or DM-who
controls that creature decides the order ...
The second attack happens after the first is fully resolved.
Rules designer Jeremy Crawford addressed this question in an unofficial tweet from June 2015:
Eldritch Blast: are the attacks resolved in parallel or sequence? Do you have to pick all the targets first before rolling?
Multiple attacks on the same turn aren't simultaneous, unless a
feature or spell ...
Color spray does not deal any damage at all
The color spray spell description states (emphasis mine):
Roll 6d10; the total is how many hit points of creatures this spell can affect. Creatures ... are affected in ascending order of their current hit points (ignoring unconscious creatures and creatures that can't see).
Starting with the creature that has the ...
They seem to happen at the same time, but there are windows for things to happen in between.
Both getting hit and taking damage are separate from each other as they can happen separately as well, not only as a combined event. You can get hit without taking damage and you can take damage without getting hit.
Getting hit and taking damage can be used for ...
You will first need to check if a duplicate is attacked before applying other effects.
Mirror Images states:
...roll a d20 to determine whether the attack instead targets one of your duplicates...A duplicate can be destroyed only by an attack that hits it. It ignores all other damage and effects.
Among the Dead specifically states (emphasis mine):
The timing doesn't matter: temporary HP does not stack
It doesn't matter how many different abilities the character triggers simultaneously that grant them temporary HP, they cannot be added together.
Temporary hit points aren’t cumulative. If you have temporary hit points and receive more of them, you don’t add them together, unless a game feature says you ...
The creature takes damage from both
Everybody is quoting the DMG on spell effects, but that is completely irrelevant here because nobody is trying to overlap moonbeams over each-other.
If the question was 'can I cast two Moonbeams on top of each other and have a creature take damage twice?', the answer is, indeed, no, because you can't overlap spell effects, ...
The attacks are resolved one at a time
Each beam of eldritch blast involves a separate attack roll and is resolved separately
This is clear from the spell description:
The spell creates more than one beam when you reach higher levels: [...] Make a separate attack roll for each beam.
Thus, we can refer to the section on "Making An Attack":
The concentration check occurs first
When you take damage, you make the Constitution saving throw to maintain concentration. This is a concurrent event. In contrast, reactions always take place after the trigger unless a timing is specified otherwise (Dungeon Master's Guide):
If a reaction has no timing specified, or the timing is unclear, the reaction ...