Weird, I have just the logicboard attached and took the broken bd drive out (So there is no bd drive in my PS3 anymore at all) since then I was still able to Update to every normal CFW without any issues and all games and apps running fine. (PS1, PS2, PS3, PSP all work) The only difference is...
I wonder how it is possible to update to OFW "by accident" lol I mean I have to start the update manually, since the PS3 not Update himself without any confirmation.
I can't talk for original PS2 discs, since my bd-player in the ps3 is not functional, but PS2 iso backups are running just fine without any issue using webman or multiman.
I guess so, since it's mentioned in the changelog that you can install this CFW over any other CFW. Just no OFW of course. I updated from Ferror 4.83 and it worked perfectly.