I don't believe apps are backup'd only the apps settings and data

When you create a backup, it doesn't really backup all your applications. That would require insane amounts of storage, so instead, it just saves the app's settings and data and automatically re-installs them after the restore is successful. So if the developers still provide an app version that supports your current iOS then go for it. if not. then nothing to be done really.

Install an app on an earlier version of iOS or OS X - Apple Support

If you‘re missing apps or data after restoring from an iCloud Backup that you made with iOS 9

If you made an iCloud backup of a previous device that had iOS 9, use these steps before restoring your new device from a backup. You can also get help if you're missing any apps or data after restoring from a backup that you made in iOS 9.

We have discovered an issue that affects iCloud backups created from iOS 9 where some apps from the App Store will only restore to the same model of iOS device. We reprocessed the impacted apps and made updated versions of them that are available for customers.

Before restoring to a new iOS device, make sure that all of your apps are up to date and then make a fresh backup. This is important, because it ensures that all of your apps and their associated data are correctly moved to your new iPhone or iPad.

Update your apps and back up your previous device again

Before you set up a new device from an iCloud backup that you made in iOS 9, follow these steps:

1. On your previous device, open the App Store app and tap Updates.
2. Update all of your apps by tapping Update All.
3. Wait for all of your apps to finish updating. Then go to Settings > iCloud > Backup. Make sure that iCloud Backup is turned on.
4. Tap Back Up Now and remain on this screen until the process completes. Stay connected to Wi-Fi until the backup is finished.
5. Then check that your backup completed: Tap Settings > iCloud > Storage > Manage Storage, then select your device. The backup that you just made should appear in the details with the time and backup size.
6. Now you can set up your new device from this backup.

If data or apps are missing after restoring from a backup that you made in iOS 9

The apps on your previous device might not have been updated before you backed up. If that backup was used to set up your new device and you're missing apps or data, here's what you need to do:

1. Follow the steps above to update the apps on your previous device and back it up again.
2. On your new device, tap Settings > General > Reset. Tap Erase all Content & Settings. This will delete any content that's currently on your device.
3. Now you can set up your new device again using the backup that you just made of your previous device.