sorry to ask...

my phone...
iphone 3g singtel set
bootloader version 05.09
baseband version 02.11.07
os version 2.1
current using celcom 3g sim card

my question...
better to update or restore?
insert sim card or not in the upadate or restore process?
if update or restore, baseband change or not? if change, what baseband will it be?
can jailbrake or not coz with bootloader 05.09 cannot downgrade baseband right?
i read from page 1 till end but find different answer... please help...