Is the free app monetization scheme through donations allowed or not?

Question

Google Play

There are many applications in the play with donations to the developer for the development of the program or expression of gratitude.
But re-reading https://play.google.com/intl/ru_ALL/about/monetiza...
The Google Play content payment system is not supported for the following types of goods and services:
One-time transfer of funds. This includes loans, online auctions and donations.
or in English
One time-payments, including peer-to-peer payments, online auctions, and donations.
So "buy me coffe" is a violation or not?
Or specifically pushed to
Allowed:
Additional features or special content. For example, the ability to view the application without adsor features not available in the free version.

Answer 1

Yes it is allowed, but about this:
Here it says that you can make a purchase, let's say remove all ads for $ 2, or you can sell levels that are not in the free version of your game