which one should I choose from backup:1 )back up most important or 2) back up all of the data ?? My iPhone doen't turn on

My iPhone can't turn on after turning off about 2 hours. I can see apple mark on the screen but doesn't do anything.

Then unfortunately, you will not be able to back up the phone at all. Backups have to take place....before....problems occur. It's too late to back up your phone now.

If you use iCloud for backups, then you can use back up most important information. If you do not use iCloud for backups, then you can choose the back up all option. You are safer with using the back up all option.

The other thing is that you may not be able to backup your iPhone to a computer if it does not completely boot up to the Home Screen. If this happens, then you will have to go the Apple Store without creating a backup.

Axel F.