JEE

Yes, it's compulsory to score 75% for general category students and for SC/ST, it is 65%.
All the best.

No, they take admission through MHTCET exam conducted by Maharashtra government but if some seats are left then they can take admission through JEE Mains marks.

Colleges like National Institute Of Technology (NITs), Govt Funded Technical Institute (GFTIs) are participating colleges through JOSAA counselling which you will get.
But some of the private colleges also take admission on the basis of JEE Mains rank but not through JOSAA counselling.

Yes, you can take admission easily just try to contact to college for all the details about admission and counseling process.

Yes, Sad but your 2 chances are over for JEE advanced, but don't worry you still have one chance left for JEE Mains.
Prepare for it and you must be in some NITs.
Best of luck.

Your chances are very low. You should try next year.

The average cut-off is 110 for general category.

Dear Ankush, first of all, you have to apply for REAP for admission in Rajasthan for B.Tech. Before filling in REAP, you should visit the best engineering colleges in Jaipur where better placements, nice labs, best faculty members and opportunities are provided for start up through incubation center like that Anand International College of Engineering.

Chances are very low as it depends upon your JEE rank.

You have qualified which is very good. This will bring a confidence in yourself so I think you should drop one year and try your best to crack JEE Advanced which is your target.
All the very best.