I(21 yr old) have squint(extropia) in my left eye.i have done patching for 10 days.now sudden when i rorate my left eye i can see it blurry i.e. 6/12.

Not necessary nor: Useful to patch your eye. At your age it will not improve exotropia nor the lazy eye. Blurring probably unrelated to patching. But if it persist see your ophthalmologist.

Supression: Your outward deviating eye is supressed, otherwise you would be seeing double all the time. Patching can bring the vision in the supressed eye up to the best level it had prior to become 8 years of age (when everything gets fixed). But the supression will continue preventing double vision.