The "compatibility" variable is unrelated to the script language and won't give an error. But you won't normally need it unless you're using A6 templates. In all other cases better check your script first - if it doesn't work with 7.82, there's most likely something wrong with it.

You can use the lite-C shooter tutorial as experimental kit for developing scripts with walking and collision detection. Also, look in the manual for moving with gravity examples.