The problem with driving through grass with a Heng Long or a Taigen Tank especially one fitted with metal tracks is that the sprockets will get grass wrapped around them and stall the motors and because the makers of these Tanks have not built a fuse or cut out into the control board the Tank will stop because of the overload on the motors and there is a good chance that the famous "Magic Smoke" will come out of the MFU and that is game over.
Carpet in general is fine, The only problem I have ever had with using that surface was when she who must be obeyed caught me doing it, Paving and garage hard standing as well as compacted earth is perfect but wear and tear is inevitable,
I would avoid water although as "Cruis" will advise you as long as the control board is isolated from it all should be fine.
Soft sand is the killer it gets everywhere and it just grinds away any moving surface it comes into contact with.