How will the  ADIT exams be held in 2021 by the CIOT?

The CIOT has announced that all ADIT exams in June 2021 will be examined remotely via Exam4. So using your own laptop/desktop you can sit the exams at a location of your choice, such as your home or office.

Can I avail any exemption in ADIT exam?

No, there is no such relief available presently by the CIOT institute. So all 3 modules are essential part to accomplish with

ADIT would provide me any exemption in other tax qualification ?

Yes,  if you qualify 2.09 option paper, you would be able to claim relevant exemption in CTA qualification please find more info from institute here.