Chances of u getting admission  in skit with 36 in jee mains n 83.2% in 12th are extremely high .You can easily get ECE or mech not sure about jecrc .but dude these are private colleges so u can get admitted here no matter how much u score in mains. You can fill both your mains score as well as your 12 th score as there is 50-50 percent of total intake through mains and through 12th board so overall filling both of them is benefficial as it will only increase your chances of getting a good college.

Although the cutoffs aren't out yet but to get admission in any of the mentioned college you need to score atleast 60-70 marks in mains (for general category) so as you told you're from obc so that would help you to get admission though you might not be able to get the core branches like CSE or ECE.