I am going into Class 12 and I am starting my JEE preparations now in the month of Feburary. I only have 10 months left for JEE 2021. Is that enough time to crack JEE mains and advanced without coaching? I have HC verma, Objective Mathermatics by RD Sharma, and Arihant Jee Chemistry Master Resource

Yes, you can do it. Better late than never.
10 months is a lot of time, just dont get distracted.
Clear all your concepts and practice more and more numericals and past year papers.
And most important thing in preparation is time management, if you manage your time perfectly and divide it for all the three subjects, you will do wonders.
And one more thing, the topics which you think are difficult, dont leave them for the end otherwise they will create problems at the end moment, so clear them in the early phase and practice them.
If you will manage your syllabus and time well, 10 months will be enough to get a good rank that will land you in a good college.
These books are good. For chemistry, you must cover NCERT also as sometimes direct questions are asked from it.
JEE Mains is comparatively easier to crack, you can do it easily of you start right now.
For advanced, you must work harder.
So just focus and study hard, but dont study blindly that once you start studying, you are continuosly studying for hours and hours. Take small breaks to refresh your mind and also have a balanced diet and a sound sleep as it will help you boost your concentration and focus.
Best of luck!!!!