debian – Block all DNS requests only allow requests to my own DNS server

I am Using Pihole installed on a Raspberry PI to block advertisements but to be certain that DNS requests that are hardcoded in certain programs are blocked as well, I would like to block all DNS requests with the exception of PiHole’s IP address.

I have my PiHole installed on and to add, it is possible to LOG DNS requests that are anything other than ? I would like to know when it happens, where it originates from.

many thanks in advance,