How to get Minecraft for free on Xbox One if I purchased it on the Xbox 360?

No, it used to be discounted, you could buy it for $5 if you own the 360 version, but I don't think that offer is valid anyone.

I'm not sure as i'm not an xbox player but i think the new xbox has like i don't know backwards compatibilty but in your case you'll probably have to buy it again.