African Dwarf Frog question????

OKay so my science class is giving these guys out at the end if the year and I want to take one. I already have a African Clawed Frog, but I cant keep the 2 together cause my AFC will eat the dwarf. I have a male betta in a 2.5 gallon tank. Some say you can put your frogs with bettas but im a little worried about that. My dad says no more heaters or filters cause I already have sooooo many pets in my room. So I read that these guys can live in 2.5 gallon tanks with no heater as long as the temp is above 70 and your rooms warm. My room is very small and filled with animal cages and heaters; it's very warm in my room. And I read that you don't need a filter as long as you make 25 percent water changes once a week. I want to know if I can put my frog in a plastic critter keeper. Is plastic okay- like will it put toxins or something in the water???? I only know the care of AFC frogs not the dwarfs. If I get this plastic 2.5 cage can I put gravel in it?? I know with AFC you cant cause they'll eat it but I understand that the dwarfs are more docile and won't eat every thing in their path. Also I don't have a light can I just keep the cage by the fish tank so there is light in the day???? Thank you! IUjust want to know the care of these frogs before I go out and get one:)