Sync, back-up, and restore

[mrhifi]

Hello,

Thanks in advance!

I have two 3G iPhones. Both phones are jailbroken and unlocked with Blackra1n and ultransn0w. Phone #1 has been upgraded to 4.2.1
and backed up on iTunes. iPhone1,2_4.2.1_8C148_Custom_Restore.ipsw #

I want to back-up phone #2, as I have purchases made directly to that phone.
Can I back-up phone #2 but restore it from phone #1 back-up? If so, will it upgrade the firmware?

If this works, and phone #2 has been upgraded, is there anyway to retrieve data, apps, etc from the phone #2 back-up? Or is the data lost since it is different firmware?

I need a unlock, as I m not using AT&T.

I am a newbie and could use a step by step solution if anyone has one.

Thanks a million,
mrhifi
Brad