The pilot manual for T-34 A allows spins, but as I remember if says to recover within 2 turns. The FAA was doing a seminar on spins at EAA one year and emphasized that the first part of a spin, ( I think it was 2 turns), is only the entry to a spin or the incipient stage. Many planes, if not most,will recover easily if recovery is started in this incipient phase.However, some like the T-34 get more resistant to recovery after 2 turns when the plane enters the full established phase of the spin. Then it may take longer to recover, if at all once the anti-spin corrections are put in. A P-51, for instance is reported to take a couple of turns to recover from a full spin.
Note, that only T-34A is approved for acro. The B model can do it mostly as well, but near aft cg it will not recover from the spin. That was what the Beech factory found in their testing back in the 50's. Some T-34 B owners did not want this restriction, and about back in the 90's hired a test pilot to repeat the spin tests. All was well , starting at forward cg, and moving back, but just as the factory said, once you got near the aft limit it would not recover.
Being near the aft limit of cg can be dangerous in any plane, and you should be extra careful when doing acro to be in the middle or forward part of the loading envelope.
Everyone who wants to be a complete pilot should do spin training and practice recognizing the start of a spin, ( ie an uncoordinated stall) and how to recover.
Spins can be complicated, not room to go into all here.
BUT, KNOWING A QUICK SIMPLE STALL RECOVERY PROCEDURE IS VITAL.
1. Power all the way off. (note in some planes like Pitts or P-51 even a little throttle open may prevent recovery. You have to get power off to get the nose down to get airflow over the controls.
2. Release the stick or yoke, just let go of it. ( note you need to have neutral ailerons and neutral or down elevator for recovery from an upright spin). If you just quit pulling on the control that got you into the stall/spin in the first place, the elevator will release the back pressure.
3 Push and hold full opposite rudder to the direction of the spin. Hold until the spin stops, then release the rudder.
The plane should come out of the spin nose down and accelerating and you can smoothly regain control and level flight, if you have altitude to spare. That is one reason not to do vertical acro like loops down low.