Information about transactional SMS
I mentioned by @Άνδρας the questions 2 and 3 are not related to Android.
For the first question, I suggest two methods:

Android App:

you can use an Android App that use Alarm Manager which will be executed once a day or every hour to clean up the SMS database using Content Provider.

ADB solutions:

content delete --uri content://sms --where &quot;date&gt;EPOCH_TIME&quot; 

where: EPOCH_TIME is 13 digit epoch time (milliseconds)
The command will delete all messages received after EPOCH_TIME