Distribute and licensing

...And so, between one help and another, and lots of explanations, I would have completed a small app that is linked to my Visual studio project. Now I would like to ask you experts a couple of things regarding the distribution of the app and precisely: A) I read that it could be distributed through Google Play (it's convenient, but in my case it would only serve my customers, in other cases it would not serve Nothing)
B) I need advice, a tutorial, on a procedure to be able to validate a possible revocable license, but I don't know where to start; any suggestions would be greatly appreciated.
Thank you in advance

A) Suggest you offer your app in some other way, from your own website / server...
B) This offers some good advice about how to set up a revokable licence

Hi Timai, thanks for your suggestions. I also found that link very interesting, even if a few years ago, I found myself discussing these topics with my lawyer, in relation to intellectual property, which in Italy, as regards software, is very vague and incomplete . Having said that, regardless of the regulations and the law, what I really wanted was a purely technical suggestion, because as already specified, the app will go into the hands of my current customers and will have to be optional with respect to the basic software. For this reason it was useful for me to know a system to be able to deactivate it if not actually purchased with the package.