3. Some say that a cataract should be removed only when
    it is“matured”, is that true? When is a good time?

By the time a cataract is matured, an eye's vision is most probably very very blurred. Certainly a matured cataract can still be removed at this stage, but it is also true that removal with modern techniques is more difficult and potentially more hazardous. Corneal edema will be more severe and recovery of vision may take longer. Removal of a visually significant cataract before it reaches the mature stage is now advisable. However, what constitutes “visually significant” is not an unyielding rule. A safe rule of thumb is if your cataract does not bother your eyesight, you do not need to have it removed. If you are in doubt, you should undergo a full examination with your eye doctor. If you are still in doubt, seek more opinion from a different doctor.