Just to recap:
1) in language file, wherever the left column contains 'narain' or 'karthikeyan' or any form of his name, chnage the right column to the equivalent for daniel ricciardo.
2) backup flow.bin (in system folder) and put orignal pre-patch one in there.
3) in database file, f1driver tab, change nationality id to 24 in the kartikeyan row (but do not change the name or anything else).
This should then work, (apart from the helmet and photo, and driver stats, which needs further changes, but the ones outlined above are the main ones to begin with).
Can you confirm you did these 3 steps?