First of all, LIFF is NOT A Hosting Service. LIFF is a platform for web apps provided by LINE. LIFF apps can help developers (especially web developers) to interact with the LINE Platform easily and securely. The LIFF app can use such data to provide features that utilize user information and send messages on the user's behalf.
However since you asking about backups, here's some of my solutions.
Have you tried to use git or Version Control System to manage your LIFF app versioning? If you haven't make sure to take a try. This could help you rollback your app to it's previous version if the latest version didn't work well.
Have you tried to use an automatic backup provided by your hosting service? Most hosting service provide a periodical backup. You could use this as well.
Thank you! Hope this helps.