021-002 after passing 010-002.
I cleared my QT ESSENTIAL-010-002 (not currently on Qt certification official page but available on Pearson VUE) certification exam. And now I want to take Widget UI AND APPLICATION ENGINE WITH QT - 021-002 (currently on Qt certification official page as well as available on Pearson VUE) certification exam to receive certified Qt C++ Specialist certification. So Is it mandatory to clear Qt and QML Essentials-010-003 as given in 021-002 curriculum Or I can go for Widget UI AND APPLICATION ENGINE WITH QT - 021-002 now to receive certified Qt C++ Specialist certificate.
If I understand your post correctly then you are asking if you can become a Qt specialist if you succeed in 2 Qt developer tests instead of taking the Qt specialist exam?
AFAIK you have to take the Qt specialist to become a Qt specialist. A lot of Qt specialists have taken only one Qt developer exam and then went for the Qt Specialist title. I don't have statistics on this though ;-)