Some question regarding game dump and console's hackability

For a new superslim or something you may be able to use a method called "backup injection" to run backups of commercial disc games, but there are limitations I think. Google it, not very sure myself.

If you accidentally install OFW over CFW you need to downgrade again.

Yes, just copying the contents of a disc via Multiman, FTP or whatever works. It is by far the easiest method as you only need to ctrl+c and ctrl+v basically.

The rest is answered here https://rpcs3.net/quickstart