Q: I5 froze, needs to be restored.How can I back it up first?

IF you have backed up to a particular computer - plugging the iPhone into that computer usually causes recognition with an offer to backup before the restore

If that option is not available then you are very likely to lose your contents

Erase your device with iTunes

If you've synced your device with iTunes, you can restore your device.

1. Connect your device to the computer you synced with.(The Important prerequisite)
2. Open iTunes. If asked for a passcode, try another computer you've synced with, or use recovery mode.
3. Wait for iTunes to sync your device and make a backup. If it doesn't, learn what to do.
4. Once the sync and backup have finished,click Restore [your device].
   
5. When you reach the Set Up screen while restoring your iOS device, tap Restore from iTunes backup.
6. Select your device in iTunes. Look at the date and size of each backup and pick the most relevant one.