Legal Question in Banking Law in India

Yes.

Assigning job responsbility is prerogative of service and it is upto your reporting manager to decide which profile is to be given to you as per your grade/scale and prevailing service rules.

You may make a written presentation to your reporting manager with reasons. It is worth mention here that you yourself want to declare that you are incapable of handling a given profile, which, apart from the possibility of getting your profile changed, will never impart positive thing for your ability to do work.

You should make yourself strong enough to accept challenges.

The employer has to decide what work to assign. If an employee whether by his or her ineptitude does not handle the work entrusted to him/her, it will brand him/her inefficient. No doubt any employee can request to be excused from the work assigned to him/her due to innate incapacity to handle the same. But that will be at the cost of he or she being fired from the job.

No, if he has was appointed as a "cashier".