Is it possible to submit the update for review, but not have it released immediately after it gets approved
Yes. It's possible to do so.
When submitting your app for review on App Store Connect, simply select the option to manually release the app instead of automatically release. This way, once the app is approved by Apple, it is kept at hold for release ...
With an old version iTunes on a computer you can download the current version there. Once you go back to you iPad you can download the older version.
How to get the version iTunes you need.
The process[ ignore the blurb at the top which says you cannot ]:
The answer depends on what you mean by "making the same app for iPad".
If you mean that you're going to take the app (its source code) and make it compatible with both the iPhone and the iPad at the same time - and then publish that on the App Store for both platforms - then yes, you can do that. When you change your Info.plist to indicate that you support ...
If you have the app binary IPA cached and ready to install, yes you can try that by wiping the device, reload the data and only restore the app version you control.
This is not something that’s been easy or even possible for most people without prior setup work in the past few years as iTunes no longer manages local IPA downloads.
ground control might ...