Your code will be 02 if you belong to any other State except for Karnataka. Code 02 says: The Higher/Senior Secondary Examination or the Indian School Certificate Examination which is equivalent to 10+2 Higher/Senior Secondary Examination after a period of 12 years study, the last two years of such study comprising of Physics, Chemistry, Biology/Bio-technology (which shall include practical tests in these subjects) and Mathematics or any other elective subject with English at a level not less than the core course for English as prescribed by the National Council of Educational Research and Training after introduction of the 10+2+3 educational structure as recommended by the National Committee on Education.

But of you belong to Karnataka, the code will be 03.

And NTA has only mentioned payments through SBI/sYNDICATE/HDFC/ICICI/Paytm as payment gateways through Net Banking, Credit and Debit card, UPI as approved methods of payment. The information is available on Page 4 of the Information bulletin at: https://ntaneet.nic.in/ntaneet/ShowPdf.aspx?Type=50C9E8D5FC98727B4BBC93CF5D64A68DB647F04F&ID=AC3478D69A3C81FA62E60F5C3696165A4E5E6AC4