I had pain in right testicle six month back for 3 days.after a month it re-appeared.i don't have it now.if it was torsion, is my testicle dead now?

Only if testis gone: Testicle would have atrophied if if remained twisted from torsion & by now would have disappeared. Also pain would have continued for more than 3 days. You might have had intermeiient torsion, where testicle twists & then untwists. Can test 4 this by twisting testicle inwards (counter-clockwise 4 left testis) & twist till it hurts. If pain identical 2 both episodes was likely intermittent torsion.

Take it easy: It was not testicular torsion. Your testicle is still alive !