Hello.
Before going to  your question I want to inform you that if you are giving entrance exam for any course you can start this course only when if you have cleared this exam and from from a particular date after exam result and you are mentioning here that you want to do mass communication next year in April and you want to give entrance exam in 2021 so it is not possible to do if you want to go in any college where you can take direct admission then definitely you can do and if you want to give entrance exam in 2021  for any specific desire or purpose then you can do.
Best of luck.