Deploy vspackage in GAC ?

I read tutorial about vspackage deployment and how to generate registry using regpkg tool. It tell how to generate for codebase and assembly. And if the package targeting many version of VS then it should put in GAC.

1. But It does not tell me how to generate registry if I put in GAC ?
2. I also read that vspackage for specific version of VS should be built using same version of VS, is that true ?

It's hard to be advanced programmer