Iphone update

I am on iphone 4, v 4.2.1 jailbreaked and factory unlocked recently. I want to make sure, that if I backup and update to the latest version, I will be able to keep all my data and apps from my jailbreak. I will of course, backup, update, jailbreak and restore. Does this sound ok, is this order correct ? Assuming that my apps can run at the newest version (which ever that may be), then all my data in those apps should be there, correct ? It is very importand for me to keep some data I use all the time, that's why I have been avoiding to update. Many thanks in advance.