[Spoilers ep4] Strange plot hole in Arcane episode 4?

SPOILERS:

I love the tv-series, one of my favourite animated show ever. But several things are bothering me, maybe I missed something? I am not familiar with LoL lore.

In episode 4 Vi is part of the skateboarder gang when unmasked by Jinx.

In episode 6 nobody from the skateboarder gang recognize her when they fight and then are kidnapped?

In episode 7 Vi is surprised to see Echo behind the lead skateboarder mask.

Why sniper girl Caitlyn doesn't have to wear mask while traveling in underworld. She spent entire life up in the city. Similarly, boy with hammer does not wear the mask when capturing the factory in episode 8.

Was the scientist who trained child Viktor the same as the one who did experiments for bad guy Silco? Didn't the scientist die in the explosion of the bad guys basein episode 3? Is his disfigurement from the drug addiction or from explosion?