What if I got an offer letter from IIM Trichy but don’t want to join? Will I get a refund of Rs 20,000, which I paid to know the waitlist?

The simple answer to your question is no. If you do receive an admission offer after paying the remittance fees and are not joining of your own will, then the waitlist remittance fee will not be refunded. It will be refunded only under these circumstances 

1. If you withdraw your willingness by claiming a refund through the admission portal before the release of the admission offers
2. If you do not withdraw your willingness but do not receive admission offers also your 20000 will be refunded.

Under no other circumstances will your remittance fee be refunded.