Yeah! You have to cover up the 11 th syllabus but not first. You should prepare your 10+2 syllabus as well as the 11th syllabus in parallel. You have reduced time so now you need to be very much sincere. Practicing problems and mock test is must. You can opt for online coaching or mock series which can be a great option in your preparation. Also you should study from the correct books. Study the 10+2 syllabus in such a way that it gets covered with the boards syllabus and prepare the 11th syllabus as it is bounded only for NEET.

For NEET preparation tips you may visit:

https://medicine.careers360.com/articles/how-crack-neet-in-first-attempt

For NEET crash course from career360 you may visit:

https://learn.careers360.com/neet-crash-course-rank-booster/?icn=neet-crash-course-rank-booster&ici=neet-text-mapping

For NEET Important books you must visit:

https://medicine.careers360.com/articles/best-books-for-neet

I hope this answer helps. All the very best for your future endeavors!