scratchvanced is a closed source mod of scratch that adds a modern style ui to scratch and more blocks!
features!
Posts, posts is a feature that functions like miiverse! you could communicate with the community using it
More emojis
ugc sprites
age ratings, example:nfe
More sound effects!
settings! settings can make you customize scratch!
No, that is actually very wrong. Snap started out as a mod of scratch 1.4, but later was rewritten in javascript, so it now shares absolutely no source code with scratch.
In terms of content, yes, it does look a little like scratch 1.4 (although there is still a big difference), but it has a lot more features than scratch will ever have.
Snap is absolutely not just old scratch, snap is its own thing, only inspired by scratch.