I wanted to ask that - what would be the value of u&v in the case when the far point of myopic eye is 50cm and also when the near point of hypermetropic eye is 75 cm so in all these cases how and why to select u&v

In case of correction to a myopic eye, the object to be seen is at infinity ad its image is to be formed at the far point, so u = infinity and v = distance of far point.

In case of correction to a hypermetropic eye, the object is at least distance of distinct vision of normal eye and its image is to be seen at near point of defective eye, so u = distance of near point of normal eye and v = distance of near point of defective eye.