They implemented their own way of doing this. They don‘t use PGP. I don‘t know how it exactly works, but it‘s open source, so you can look at it yourself.

Subject lines are also not encrypted, unlike Tutanota.

Porn is illegal in Russia too.

Dude, Norway is one of the richest countries in the world.

Yes, but it still protects against data breaches. You still have to trust the provider though.