A Question.

Can i get vac banned by using external hacks when i rename the process to example skype?

I think you can, if external hack is writing to memory(check, if it has wireframe models, nosmoke, noflash, or sv_cheats bypass).
Otherwise, if it's only reading memory, it won't be banned.

There is always a chance. Just that hardly ever happens these days so... You'll be fine