Exam

Hello Submit,
One gets three chances max after 12th to appear for JEE Mains. Hence even if you take a drop for two years it will not make much difference.

Please wait for the results and then check it. However, there is very less chance that you will qualify for JEE Advanced. Since the cut-off for obc generally goes to 50-60 marks in JEE Mains. But wait till the result is out and cut-off is not declared.

Yes, you can take admission on the basis of MAT score.

You can download the PDF of the guide from Shiksha from where you can get all the things regarding the exam.
https://www.shiksha.com/university/Andhra-university-Visakhapatnam/exams/aucet

There are some chances for getting government colleges, you should try the Shiksha's JEE Mains College Predictor. The link is given below:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor?utm_source=cconnect&utm_medium=CR_JEECP&utm_campaign=6540165

KIITEE being a free entrance exam and people who may not pursue engineering also give it a try and it's conducted all over India for free so the figure is supposed to be in lakhs. I have seen students scoring rank in lacs and after a limit, ranks do not get published.

The improvement exam notification will release in July. This is totally an online process so there is not any type of difficulty. Your exam can be scheduled for next year with the board exams, without any practicals. The fee structure may be Rs. 200 per subject.
Best of luck.

Yes, still there are colleges who are taking admissions for 2018-2020 batch.

It will depend on the opening or closing rank of VITEEE. So, you must check out the last year's cut-off of VITEEE to get a clear idea of getting a seat.
Good luck.