안타깝게도 상위레벨에서 OPT 쓰셨으면 그전 레벨로는 opt 못 받습니다.
https://internationalaffairs.uchicago.edu/page/opt-optional-practical-training
You must not have used OPT at a higher degree level. For example, if you complete a Phd, then use OPT, and then complete a Master’s-level program, you will not be eligible for OPT for the Master’s level.