This looks like great amount of work. It would be really bad if you have to stop it later on.
They can also stop free games if they want to. It is their copyright and nobody is allowed to distribute their IP, no matter if you make it free or not.
The best way would be to ask them right from the beginning.
Yes they can stop it if they want , thats always a risk that Game Remaker have. But mostly its a good advertising for their product and they dont say anything.
Your right to ask them before making the game , i did always on my other remakes and only once i got a answer. It always is a risk to remake games and will alway be if you dont have the rights for it.
