Hello,
To be eligible to get admission in IITs/NITs/GFTIs a candidate must have passed 10+2 with atleast 75% aggregate (general category) for SC/ST it is 65%.
And yes you may qualify for JEE advanced as a minimum percentile of 85 or above is need to qualify JEE main.So better prepare for JEE advanced.
You can calculate your expected rank using the formula given below
(100-total percentile)*869010/100
In your case it is
(100-83.77)*869010/100=141040.
And your category rank will be around 12k-14k.
But considering 2019 JoSAA seat allotment candidates from SC category who have secured rank below 10000 got seats in NITs and GFTIs.But you have chances of getting seat if you hold a domicile of a particular state which has NITs/GFTIs.So if you mention your state we may help you further.
Also you can predict the colleges which you may get using the link below

Joint Entrance Examination (Main)

Application | Eligibility | Preparation Tips | Question Paper | Admit Card | Answer Key | Result | Accepting Colleges

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Joint Entrance Exam Advanced

Eligibility | Application | Exam Pattern | Admit Card | Preparation Tips | Answer Key | Result | Accepting Colleges

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