Hello, 

As per your requirement, i would say that yes you are eligible for improvement exam for pcmb only if you have cleared or paased all your subjecys in hs then you can apply for improvement in exam next year.

You need to first clear all your failed subjects in comparemental exam and once all are cleared you will be eligi6 for improvement in pcmb exam the nexr year. Without clearing the main exam, you can't apply for improvement.

Good luck