iCloud back up question

If you mean restore a backup, you can restore a backup to any device as long as the iOS version it is running matches or is younger than the one in the backup.

To learn how to do this, read/watch these links -->

Click on this link to discover how to 'Restore your iPhone, iPad, or iPod touch from a backup' --> https://support.apple.com/HT204184

or watch this video if you're using a Mac to do this:

https://www.youtube.com/watch?v=Jbp3gGTQygg

Some things are not stored in a backup. Click on this link and read "About missing information after you restore your iOS device with iCloud Backup" -->

https://support.apple.com/HT203768

You will not be able to restore a device running 14.2 from a backup made from a device with 14.5.

Yes.