Hi

It doesn't matter even if there is a gap of one year between your 11th and 12th if you are not doing any course right now or you are doing a graduation course but you don't have either physics or chemistry or Biology or don't have all of these three subjects then you need  to choose the code 02.

Now, here's clarification to your doubt:-

By last 2 years of their studies, it means your 11th and 12th studies. It doesn't matter even if their is gap of 1 year between 11th and 12th. Moreover, your class 11th certificate is not going to be checked anywhere ,only your class 12th passing  certificates are going to  matter.
What all matters to be eligible is that one should pass12th board examination with physics, chemistry ,biology/biotechnology and English and must have got at least  50  % in aggregate of PCB  i.e Physics, Chemistry and Biology /biotechnology in 12th examination  if belongs to general category , or   at least  40%  in aggregate of PCB if belongs to  Obc/ Sc /st category. So , if you fulfil this criteria then don't worry about your eligibility even if you have a gap of 1 year between 11th and 12th.

Now that,
You have very limited time left for your Neet 2021 examination , you should focus on your neet preparation following the below tips :-

*Go well through NCERT and master it
*Make routine or timetable :- your routine should revolve around 3 things i.e study, revise and practice
*After finishing each chapter you should practice questions, you should practise at least 80 to 100 numericals / mcqs in Each chapter
*Solve previous year NEET questions
*Once done with complete syllabus, go through NEET mock test papers

You can prepare well using our neet program  for which link is provided below

https://learn.careers360.com/knockout-neet-may /

If you have any other doubt then feel free to ask them :) we are always available to help you out and guide you

Thank you