Does PolyLoader changes sig?

So Does PolyLoader changes sig? I mean like does it add junk codes to all cpp files? Or do you need to add your own junk code then use polyloader?

Yes, polyloader's job is changing the source code/signature by adding junk code. Developers implement it in their source by poly methods (read in main thread for more info.)

Why not just add your own junk code? So much easier than using Polyloader. Polyloader is used for those who make public cheats. Because each build will be slightly unique, and will stay undetected for a longer period.