Gingerbread 2.3.6 to Jelly Bean 4.x.x



ATT Galaxy S2 SGH-i777 v.2.3.6 gingerbread rooted and unlocked.

want to upgrade to jelly bean
1) do i need to upgrade the Kernel AND the ROM or can i just flash the new ROM
2) if i need to upgrade the kernel do i NEED to do it BEFORE, AFTER or it doesn't matter
3) can i flash the rom an go directly to JB 4.x.x or do i have to go to 4.0 then to 4.x.x
4) will the phone remain rooted?
5) will the phone remain unlocked?