iOS backup, restore, reset questions...

Hey there!

Thanks for asking the community!

I'll do my best to respond to each of your questions.

jungmin224 wrote:

However, I heard on a blog that if you back up your iPhone before factory reset, factory reset, and then restore it to the backed up state, you will free up system data cache storage space! Is it true?

In the past, versions of iOS were affected by a bug causing a hidden system file, or group of files, to use up more space than necessary. This is often indicated by seeing a large portion of "Other" storage on iPhone. If this is what you're seeing with storage, then yes, you can temporarily remove said storage by backing up your data, restoring iOS, then restoring your backed up data to the phone.

Apple has addressed this in a more permanent solution in an update. More information can be seen on their webpage: Clear Other storage on your iPhone or iPad - Apple Support

jungmin224 wrote:

In fact, speaking of computers, if there are many apps before backing up, it takes up a lot of space! If I restore it to the point in time when it was backed up, wouldn't it be restored to a full capacity?

If you're referring to Time Machine backups here, you're correct! The more apps you have on Mac, the bigger your backup will be. This is also the case if you have a folder that frequently has a lot of changes made to it, like a large Adobe file or a virtual machine. Time Machine gives you the option to restore anywhere from your first backup on your disk, to your most recent backup.

If Time Machine hasn't backed up recently, then restoring that backup would not include more recent data. The same can be said for data on your iOS devices, if you don't have enough space in iCloud to back up, then a restore will only include what was in the most recent backup. You would fortunately get any recent documents being synced with iCloud Drive.