Not following you here.
During debug, the Pi-Hole is tested to see if it can resolve a known blocked domain (which is chosen from your gravity list) using both the loopback address and the IP of the Pi-Hole. Then, a known good domain is requested via Google DNS to verify that the Pi can reach the internet. In your debug log, it looks like this. This shows that your Pi-Hole is working properly. Everything in your debug log is normal.
*** [ DIAGNOSING ]: Name resolution (IPv4) using a random blocked domain and a known ad-serving domain
[✓] bor-bogdanych.com is 0.0.0.0 via localhost (127.0.0.1)
[✓] bor-bogdanych.com is 0.0.0.0 via Pi-hole (192.168.2.50)
[✓] doubleclick.com is 172.217.1.206 via a remote, public DNS server (8.8.8.8)
If you are seeing ads, it is likely that there is another DNS path that clients are using, bypassing Pi-Hole.
Typically, no. If you have the DNS filter set this way, some or all of your DNS traffic will go directly to OpenDNS and not through Pi-Hole.