I'm not 100% on some of the stuff here, but here's what i think you can do.
1. Not that i'm aware of (not 100%)
2. You can play PS1 games released on the PSN, not ISO's
4. I believe you can.
5. Web browser works without the PSN, dont know about YouTube HD.
6. You have homebrew apps, i dont think there's plugins like on the PSP though (could be wrong)
7. Works the same as a non hacked PS3.
8. Yes, install the showtime media player (included with Multiman)