I want to downgrade my ipad back to iOS16

The ability to restore an earlier version of iOS/iPadOS is limited - but is possible in certain circumstances.  While the procedure is not trivial, it is currently possible to restore iPadOS 16.7.

All System Updates are digitally signed by Apple - and can only be installed whilst the digital signatures remain valid. After release of a new iOS/iPadOS version, the immediately preceding version continues to be digitally signed by Apple - however, usually within a few days, Apple will revoke the digital certificate with which the earlier version is signed. After a major update, such as the initial release of iPadOS 17 - where both iPadOS 16.x and 17.x are maintained in parallel as production versions - the period that the preceding version is signed may be longer.

Reversion to an earlier version will entail the use of “DFU” mode to reinstall the previous version; all locally stored data will be wiped. If you have an existing iCloud or iTunes backup of your data, your data can be restored after reinstalling the previous version of iOS/iPadOS. You’ll need access to a PC (with iTunes for Windows installed) or a Mac (with iTunes or Finder - as appropriate for the installed version of macOS).

Be aware, that you can only restore an iCloud backup that was made for the version that you have reinstalled - or to a later version of the OS. As such, if intending to restore iPadOS 16.7, you’ll not be able to install a backup that was made using iPadOS 17.x.

So as to avoid unnecessary description of the process, iMore have a useful article that describes the procedure of restoring an earlier version. The article refers to a different versions of iOS, but the process is the same.

https://www.imore.com/how-to-iphone-ipad-dfu-mode

After you have reinstalled iPadOS 16.7, you’ll be able to restore your [compatible] backup to your iPad:

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

You cannot downgrade iOS devices. Your iPad will still sync with your Mac.