is career 360 rank pridictor perfect as it is pridicting my jee advance rank to be around 17000 to 21000 on 90 marks from sc category

It is approximately the same some time and some time vary with a huge margin....
As it will depend on previous year data, if the cutoff vary rank will vary with a huge margin

First of all no tool can tell your actual rank before the results, what Careers360 JEE Advanced Rank Predictor doing is we are taking past data into consideration and based on different statistical and prediction algorithms they are predicting the ranks, which can be said is close to the actual ranks.

Even full analysis was done, where the Rank predictor tools present in the market for JEE Advanced 2016 was compared with the competitors and actual results of the students, with proper analysis it came out that Careers360 JEE Advanced Rank Predictor was 75% in range of actual ranks .

This is an approx ranking and is based on previous year data and ranking. It can be somewhat to the actual rank but not accurate as each year cutoff varies.

Also with this score you have less chances to get NIT's.

All the best!

Yes it is correct it is predicting ur general open rank