i tried it and try to use my latest backup ... if i take an older backup will all progresses in games be erased?
This happens to be a serious RTFM problem. Do the math. 1.5+6+Default software= 8GB. i.e. You've run out of space. Delete stuff you don't need.
This is not usual - usually after a successful sync, most of "other" gets properly categorized. If your backup is recent, I would recommend that. If not, reboot the device and re-sync. Make sure you "transfer purchases" from the device first. Be sure to let the backup complete - don't skip it!
Happened to me once. Just resync. For some reason, iTunes wouldn't recognize my iPod as an iPod but just as a flash drive, but it was still full.
Yep, there's about 2 gigs of pre-installed stuff. I remember when I got my 16 gig and saw I had 14.53 gigs free space, I thought false advertising! Lol