Can I restore an old iCloud backup after setting up a new iPhone?
if i back up my old phone after i already set up a new one, will it transfer over?
[Re-Titled by Moderator]
No. You would need to start over on setting up your new iPhone and use the backup when you do that.
To start over, use the following instructions:
To erase your device that's using iOS or iPadOS 15 or later, tap Settings > General > Transfer or Reset [Device] > Erase All Content and Settings. On iOS or iPadOS 14 or earlier, tap Settings > General > Reset > Erase All Content and Settings. This erases all data on your device. After you erase it, your device restarts and the "Hello" screen appears.
Then to set it up again using a backup to a computer, see: Use the Finder, Apple Devices, or iTunes to transfer data from your previous iOS device to your new iPhone or iPad - Apple Support
or if you backed up to iCloud use: Use iCloud to transfer data from your previous iOS or iPadOS device to your new iPhone or iPad - Apple Support
Another option that you can use without a backup (but you should still backup first) is Use Quick Start to transfer data to a new iPhone or iPad - Apple Support
See information about all 3 of the above methods in Transfer data from your previous iOS or iPadOS device to your new iPhone or iPad - Apple Support