This homebrew is extremely unbalanced
1. Ability Scores
A +4 to Dexterity makes this race unbalanced. In a point buy system the character would start with 19 Dexterity and be able to hit 20 Dexterity and 16 Constitution at Level 4. That makes this race ideal for a Rogue, Monk, or a Dexterity-based Fighter/Ranger. This is way ahead of any other race including the very strong Mountain Dwarf at +2 increases to Strength and Constitution. Strength and charisma are often dump stats (ability scores that are used for low ability scores to allow other scores to be high) for Dexterity characters because the saving throws for these two stats are much less important than the primary saves of Constitution, Dexterity, and Wisdom. In addition, Dexterity is widely considered to be the most important ability score in the game because it affects to hit, damage, armor class, a very common saving throw, initiative rolls, and several useful proficiencies. The only downside is the poor social proficiencies the character would have from a low charisma and a low carrying capacity from low strength. A dice roll character generation could easily (actually likely) result in a 20 Dexterity at level 1.
The only way I would see allowing a +4 for a primary stat (Strength, Dexterity, Wisdom, Intelligence, or Charisma) would be to take -2's in in two of the primary save stats (Dexterity, Constitution, or Wisdom). You could view this as an extreme form of Min-Maxing (where some stats are improved to the maximum at the expense of other stats deemed less important to the character build). Even here I would hesitate to allow such a strong Dexterity. A +4 Dexterity puts the 4th level character at a +1 for armor class, to-hit, and damage, versus other races, which is the equivalent of giving the character a +1 weapon and +1 armor, plus improved proficiencies and saves.
2. Movement
120 foot movement is way beyond any other race (the next fastest is at 35 feet). This is beyond high level monks. Being able to kite around (move at will around the periphery) the battlefield is way too powerful.
3. Blurred movement
Imparting disadvantage against all incoming attacks is equivalent to an always-on Cloak of Displacement (a rare item already). There are actually no magic items available that are this strong, so this would be a Legendary item. Disadvantage is generally considered to be a -5 to hit for enemies. This alone makes the race over-powered.
4. Quickling Evasion
This build already has the strongest Dexterity saves and now it gains the 7th level Rogue Evasion feature at level 1. This is also something that no other race can do.
5. The disadvantageous features are not to the same level as the advantageous ones
Age seldom comes into play in a 5e campaign (players can easily reach level 20 within a game year). Slight build means the character can't move life or carry very much, but this is a minor thing in a party where a fighter, barbarian, or paladin is assured of a good strength score.
6. Sneaky Quicklingses
Points just for the title.
Conclusion: This race is completely over-powered.