Hey,
Yes, you can appear in IISER exam. Candidates can apply to IISER by one of these three channels-:
• KVYP Channel: Kishore vaigyanik protsahan yojna
• JEE Channel: Joint entrance examination 
• SCB Channel: State and Central Board channel. Students who pass their 12 boards in science stream(PCM or PCB) with marks equal or above the cut off percentage in their respective boards are eligible to apply through SCB.

There is an aptitude test for SCB candidates which consists of Multiple choice questions in four subjects-: Physics, Chemistry, Mathematics, Biology.

All the best!