"Typical examples of commercial licensees include device manufacturers embedding Mono in hardware where the user is not able to independently upgrade the Mono virtual machine from the source code"
This rules out Android and iOS. Unity has a free version but also has restrictions:
Unity Free, which include the free platform add-on products, may not be licensed or used by a commercial entity with annual gross revenues (based on prior fiscal year) in excess of US$100,000, or by an educational, academic, non-profit or government entity with a total annual budget for the entire entity (based on prior fiscal year) in excess of US$100,000.
So, again, make sure you are doing your research well, because you might end up in an unexpected situation.
It is easier to write an incorrect program than understand a correct one.