Restoring an iPad from iPhone back up - will it Include all apps on iPhone.

iCloud and iTunes backups do not contain the App - but will contain a backup of any data associated with an App.

Upon restoring a backup to a device, any Apps associated with the backup will be downloaded from the App Store if:

• the AppleID account has record of the App purchase
• the App remains available from the App Store
• the App is compatible with both the device and the installed iOS/iPadOS version

In theory, a device backup for an iPhone can be restored to an iPad of the same iOS/iPadOS version - and vice-versa - and compatible/available Apps downloaded during the restore process.

I hope this is helpful in providing some clarity.

Maybe. I know that is not what you want to hear, but with the changes in how backups hold apps and information for apps, when you restore a backup, it usually will download information from the App Store again. With it not being available it may not download. Is this an iTunes or iCloud backup? From what I've read about others with apps that are no longer available, it won't work, but there is no harm in trying. It cannot hurt anything.

I don’t think so.

It used to be that you could back up apps locally and thus restore apps no longer in the App Store, but that ability went away quite some time ago and all apps are now redownloaded from the App Store.

Add to this the extra complication that not all phone apps work on iPads and vice versa (some are universal, some are not, and now with phones running iOS13 and iPads running iPadOS (different operating systems) there may be other issues.

You won’t know for sure until you try but I do think you’ll be out of luck for those apps no longer in the App Store.