Does it come with extra skins since you purchased it
Compared to the iOS and android free versions, yes, but there are still buyable skins and things. You can get around this and use all skins with an among us editor, which you can find just by searching "Among us editor" and clicking on the github link.
TL;DR: You get ones not available on the free version, but you still have to pay for some unless you cheat.
No problem! Here is a link to a good editor if you need one: https://github.com/Koupah/Among-Us-Editor
(Again, if you can, I would recommend supporting the developers)
(This application requires java)