The exam pattern for JEE Advanced is never disclosed by the IITs. However you can always get an idea from the previous year question papers to prepare. Check the exam pattern gauged from past years here. https://engineering.careers360.com/articles/jee-advanced-exam-pattern

This year things may be slightly different as the exam is going online

To take admission in IITs/NITs/IIITs and GFTIs you should have 75% marks in your board exam or you should be in top 20 percentile. For ST/SC you should have 65% marks. 

If you want to take admission in DTU and NSIT you should have aggregate 60% marks in P/C/M. There

In order to solve questions it is very important that your basics are clear. If your concepts are clear you can solve tricky questions as well. 

In order to approach your paper it is very important that you should analyse your paper first. Try to answer easy and avearge questions

JEE Advanced maximum are not defined :

Maximum Marks vary every year like below:

2017- 366 

2016- 372

2015 - 504

2014 - 360

So, it is difficult to predict marks as exam pattern and marks change every year but you should score more than 50% marks to get good

You need to score around more than 170 marks in WBJEE to get a rank under 100-200. To know about the WBJEE cutoff with given below link.

WBJEE Cutoff

Good Luck!

You can make your time table on your own according to your comfort. 

You should focus on your regular course by completing simultaneously chapters which are left.

Make sure you understand the basics properly you can take help of NCERT books. 

If you have any doubt clear it with the

Yes you can appear for JEE Main. However you have to qualify for JEE Advanced and apply for admissions to the IITs as only IIts consider the admissions for diploma holders. JEE Mian is just the eligibility test. You cannot apply for NITs through JEE Main.