Your code will be 03. Code 03 says that: The Intermediate/Pre-degree Examination in Science of an Indian University/Board or other recognised examining body with Physics, Chemistry, Biology /Biotechnology (which shall include practical test in these subjects) and also English as a compulsory subject

So though you have completed your 12th in 2018 and haven't appeared for NEET in these 2 years, your code will be 03 unless you have joined some other course. In that case, the code will change based on your current qualification. So do let us know if you have joined any other course after your 12th in 2018.

Code 02 is for Candidates who have completed their 12th in 2019. But in your case you have completed your 12th in 2018. But you haven't joined any course. So you should ideally fall under Code 03.