Older software

It is not possible to restore an earlier version of iOS/iPadOS. 

All versions are digitally signed by Apple; digital signatures of old versions of System Software are revoked by Apple soon after release of an updated version of the Operating System. As all digital signatures are verified as valid prior to installation, older versions cannot be (re)installed.

If you are reliant upon software that does not work with the currently installed version of iOS/iPadOS, you are totally dependent upon the Developer updating/fixing their App.

How to contact an app developer – Apple Support

No.

That time has long since passed.

Also, Apple has no procedures NOR provisions for downgrading/reverting to a previous iOS/iPadOS upgrade/update version.

iOS/iPadOS device upgrades/updates are, usually, one way. Forward NOT backwards.

Sorry.

No and this is because Apple does not support downgrading from a higher iOS version to a lower iOS version.

Axel F.