I had a crasy idea; here it is. Let's say I'm flying an 80" Extra 300s with a .6 nitro motor in it. I then go into a dive straight down with full throttle util my plane is 30 ft. off the ground. I then pull up, and go straight up until I reach a complete stall so the plane is not moving at all. Then, instead of letting the nose of the plane fall to point down and regain speed, I cut the motor, then I move the right controll stick, on the remote, to the top so as the elevator flippers point toward the bottom of the craft. Then (here's the crasy part) could I, by careful maneuvers with the control surfaces, cause the plane to start a reverse momentum and start gliding down backward for at least a few seconds?
The plane would be extremely unstable in reverse - like trying to throw a dart with the fins first.
It's not really the same thing, but some indoor models with reverse thrust do manage to fly backwards for short distances at low speed.
Another example is RC helicopters flying backwards at high speed, despite a vertical tail - this is only possible because the tail gyro can react very quickly, and the tail rotor works in either direction. It wasn't possible before heading-hold gyros were available.
However for the sort of model you're talking about, you'd not only need superhuman reflexes, but the loads on the control surfaces could overpower the servos.
The maneuver you describe is called a "tailslide" -- I've seen it done in full size aircraft, but it virtually always ends in a "whipstall" (the alternative is advancing power after a short slide and pulling up with thrust/weight greater than 1:1, if you have that much power available). Because the airplane is unstable in that direction (both in pitch and yaw), it requires the reflexes of a computer to keep it correctly lined up with the airflow while it gathers any significant speed.
As soon as the stabilizer gets far enough out of line that you can't overcome it with elevator input (too little or too late), it will flip nose first -- in a full size aircraft, this can pull enough G load to damage the airframe or injure the pilot. Most models, even pretty large ones, can take more G than a full size, so the bigger issue is that, since you're doing this fairly close to the ground, you may crash while trying to recover from the whipstall.
At the very least, practice with some altitude cushion.