(preferably) free app to lock iPhone for predetermined periods of time Reading here

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my understanding is that I can ask question about third-party Apple software, as long as I don't ask "which is your favourite app to do something". However, there is also a Software Recommendations site on Stack Exchange so I'm a bit confused as to whether my question is on-topic or not...please migrate my question to Software Recommendations if it's off-topic here.

Concerning duplicates, I've searched the site and I found

Any way to automatically lock *Me* out from *My Own* iPhone for a specific amount of time?

The answers don't satisfy me, because I don't want to jailbreak my phone. I know for sure that today there are some paid apps which don't require jailbreaking and allow me to disable the Internet connection (both WiFi and cellular data, but not cellular voice) with a recurring schedule, for example from 9 PM to 8 AM. Are there also free apps?

Requirements:


the app should "resist" attemps to force the block, but it's not necessary that it's 100% tampering-proof. Its main use will be preventing kids to access the Internet after a certain hour, it's not like it must resist hacker attacks :-)
the schedule should be configurable
it should be possible (but not easy) to overcome the block if needed. For example, one evening it may be necessary to use the cell phone after dinner. In that case, for example pressing a button and then waiting 15 minutes with the screen on should allow to stop the block.


If free apps don't exist or have glaring flaws, I will accept suggestions for paid apps, but I'd prefer free apps.
There are no App Store apps which are able to prevent other apps from being opened. Apple does not provide such functionality to apps, so you will not be able to find an app which is able to do this.

Preventing apps from being used is something the OS can do for some native apps. See Settings → General → Restrictions for being able to set a passcode to prevent access to certain functionality on the device.