@Riz J 20th date is ex date. Means who are holding shares of RIL on are entitled for 1:1 share of JFSL.
Now answer of your query:
1. When these shares of JFSL will be credited in demat account is not known.
2. We need to wait for the listing of this new company.
Now both these points are unknown to the market. So, trading of these shares can't be traded in stock market. Neither these shares are credited in demat account nor listed. No question of dealing in Share Market.
Giving you examples of NMDC and Shipping Corporation of India. You can go through these and know the facts.