Yes , it’s possible .
I have done it.
You have ample amount of time, utilize it properly.
Prepare your syllabus for class 12 till your boards along with solving mcqs.
For Biology : Read Ncert , practice from NEET GUIDE / NCERT FINGERTIPS of Mtg publication. This will help you to be more accurate in understanding what you have gained.
For Chemistry: go through some good book , like modern abc of chemistry and practice mcq from this book only. This will help you to cover your theory and mcqs both.
For Physics : Go for some board oriented book , practice derivations and solved examples. You need understanding rather than mugging. You have enough time .
I think ,you will be able to score good in boards and Neet too.
For covering the syllabus of class 11th , just after the last board exam , start with physics of class 11th difficult topics then go with chemistry and then biology.