Q1.as you can see in this image. its showing 0.78GB space is reserved by
"other files" , how i can i access to that area as its getting higher and higher day by day ?
Q2. "check for updates" and " Restore " both options are disabled. i've no idea why is that
my phone is JB iPhone4 with ios 5.0.1 having 1.59.00 baseband....
In answer to your first question, the "other" space on your phone is taken up, mainly, by temporary files that apps create, amongst other things. You can read a little more about it here. 0.78GB is about normal for what I have most times I sync. If you want to try and reclaim some of the space, try following the instructions in the link.
Unfortunately, I've never seen blacked out restore and update options like your screenshot shows, so I can't help with that one. My guess though would be that it could be because you're jailbroken.
