What happens to my apps when I update my iOS for my jailbroken iphone 4s?

I have iphone 4S, currently running iOS 5.1.1. I'm planning on updating my iOS to 7.0.4 (the most current one), but I'm having few doubts:

1. What will happen to my apps that I installed? (non-free apps that I downloaded from installous, app cake, etc)

2. What will happen to my apps that I downloaded off Cydia? (iFile, Blutrol, etc)

3. I heard numerous rumors about how sometimes, the update for iOS will fail, and I'll have to literally erase EVERYTHING, or worse, buy a new phone. Is this actually true?

If someone can help me with these questions, or maybe guide me to the answer, I would greatly appreciate it.

-for the apps that you have installed via appcake/vshare.etc you can always use Ifunbox to backup
http://www.techjay.com/2013/03/how-to-backup-vshare-and-appcake-packages-to-itunes.html

-for apps/tweaks that have installed in cydia you can use aptbackup
http://thebigboss.org/guides-iphone-ipod-ipad/how-to-upgrade-in-itunes

and %35 of all time something is always going wrong while you update or jailbreak you phone but don't worry its really not true that people saying things like your phone will break or you need to throw it away
if anything went wrong you can always hard reset your iphone
http://www.wikihow.com/Hard-Reset-an-iPhone
and if it didn't help then you can reinstall the whole system via itunes
http://support.apple.com/.../kb/HT1808

hope you understand