Hey Jolly.

See u can give ur JEE ADVAMCED exam in the 2020 if u have not given the entrance exam this year. According to the JEE portal one aspirant can give the JEE MAINS exam for consecutively 3 years and JEE ADVANCED for 2 consecutive years until the age of 25. So if u want to givw in 2020 u should not be writing the paper this year otherwise u will only be able to give the MAINS paper in 2020.

Hope u got ur point. Ask if any query.

Good luck