For takeoff... you want a small amount of flaps . 5 deg to 7 deg deflection (about 1/4 inch on a typical .40 size plane) The idea is to make the effective angle of attack at the root higher than at the tips and reduce the chance of a wing-tip stalling befor the root.

For landing... you slowly dial in more flaps, don't just dump them down. If you dump them down with airspeed too high you get the baloon effect every time... an have a higher chance of ripping off a flap. (ripping them off is not a big concern with most models... its a huge concern full scale) Most planes need some up elevator to keep the nose up with the flaps deployed.(after the initial ballooning) Some need some down elevator to prevent the nose from rising. Its rare that one would need neither. Cessnas tend to need the up elevator.

The full scale Cessna will have a mechanism that can not deploy the flaps fast enough to violently effect the aircraft such as you describe IF the flaps are deployed within specified speed range. If you find the air speed indicator in a full scale plane, you will find it has several colored arcs on it (if its a mechanical analog dial. Newer stuff?). The main green one is normal speed range with no flaps. There will be one or more arcs that are for flap operating speeds. the top speed for flaps will be within appx 1/3 or less of the main speed arc, and the bottom flap speed will be somewhat lower than the bottom of the main arc.

The main purpose of high deflection flaps (on a light aircraft) is to allow a steeper approach without building up airspeed. They also allow you to fly slower before stalling. (how much slower is dependant on if you are trying to maintain altitude or making use of the increased sink rate...)
On a jet airliner the main purpose of flaps at any deflection is the lower required flying speed. They can nearly double the wing area with the multi-stage Fowler flaps.

When you flair for touchdown with flaps down and have the wheels touch just as the plane stalls you can end up with an extremely short roll-out. I've seen a full scale C-182 have under 100 ft roll-out on grass in light winds. (he darn near drug the tail when he touched)