DNS protected you PC...

DNS can to some extent prevent data leakage if your router has been infected and traffic redirected to it. This information is not widely disseminated because it is always explained fairly, not because they are unaware, but because there is no need for such explanation.
DNS: -
DNS: -
DNS: -

see attachment

Sorry my terrible english!

Are they always functional and do they protect?

yes, they protect mainly if we set in settings adapter network…

sorry my english!

Have a read of this and try the test if you want: DNS Leaks

DNS: - seems to be comodo DNS https://securedns.dnsbycomodo.com/
DNS: - is probably Neustar, as they say UltraDNS public https://www.publicdns.neustar/

Neustart was acaquired years ago by Comodo so these servers also belong to Comodo.