IPhone iCloud backup for ios7?

So basically ios7 is available now but I need to back up my iPhone using iCloud. I know how to do it and everything like that it's just this! Whilst it is backing up, can I open other apps and let it go on lock? And also, my iPhone is a 16gb so how long will it take to back up because when I tried this morning it wouldn't work properly and it took AGES!

I want to point at something, iCloud has a specific storage which in default is 5GB, those 5GB are not related to the 16GB you have, you can buy more storage for your device, and backing up depends on how much data and files you have, and Yes, you can lock you iPhone, or use an application while backing up on iCloud, but don't close the settings app. If you are willing to upgrade your iPhone to IOS 7, you can update it from the phone directly, it WON'T erase any data for you or any conversations you had in Whatsapp, Viber… And you can update from you computer, via updating iTunes to 11.1 because earlier versions don't support new IOS 7, then downloading the complete new software and restore or update as you whish, but restoring requires back up and I recommend for you backing up on you PC(personally I don't back up on iCloud). And I would like to tell you some more information before you update…
IOS 7 has new features, some aren't supported by iPhone 4s and iPhone 4, and if you are a jailbreaker, it seems that IOS 7 jailbreak will take a real time to be released… That is all.