Are you certain that the tape you have was recorded in a format that allows this.
You have two track - stereo one direction only
You have two track - two tracks of mono - you turn the tape around and play the other direction
You have 4 track two lots of stereo - turn tape around and play
They are not compatible, though some machines can handle a couple of formats but usually they cannot handle all possible formats
Some machines can handle several formats, but only record in one format.