Apple
Restore your iPhone, iPad, or iPod touch from a backup – Apple Support
How to back up your iPhone, iPad, and iPod touch – Apple Support
How To Back Up An iPhone or iPad: Save Photos, Messages & More | Macworld
Android
Back up or restore data on your Android device – Android Help (google.com)
Microsoft Windows
Back up and restore your PC (microsoft.com)
Apple Macintosh
How to back up your Mac – Official Apple Support
Restore your Mac from a backup – Apple Support
If you can’t back up or restore your Mac using Time Machine – Apple Support