please suggest best test series for ca final old syllabus group 2

Solve RTP/MTP under exam conditions.

Don't waste money on test series/MCQ tests.

ICAI papers itself are so big in volume that you can easily write 8-10 papers in each subject(i.e MTP-2 series for each attempt/RTP/Past year)

If you are not finding MTP's for past attempts, search in google & you will find them

For taxes alone- buy a compiler of any author solved as per latest finance act & solve those over next 45 days or so.