ps2 compatibility was removed because it contains exploits just like actual ps2 does, some of the ps2's lesser known software flaws are actually essential for it to function, so they can't be patched.
The thing is that the ps2 emulator inside a ps3 has a wide access to the system and sony is afraid of that. Not that the chocolatety ps3 scene ever gets anything done with it anyway.

and yes, also so that they can make you buy your ps2 games again for no reason.

anyways, the ps3's backup takes long because it's programmed by an idiot. The ps3 backup consists of a raw disk image of your hard drive, that is then encrypted, compressed, then split into 4gb pieces (limitation of FAT32 hdd's such as the one you need for the backup because sony are too retarded to implement NTFS or reiserFS support.) After all that spoon is done, the pieces are then garbled once more in an attempt to prevent hackers from messing with the system files that are inside.

they failed though, lol

basically 20% of the time you backup/restore is used for backing up / restoring. the remaining 80% is used to n compressing, encrypting, decrypting and uncompressing.

welcome to sony <3