Not able to convert from NFA to DFA
You are fine up to step 3 (the DFA) but your minimization is incorrect.

It's clear that the minimized DFA is not right, because both the inputs ba and ab (which are not in the original language, nor are they accepted by the DFA in step 3) lead to final state E.

Looking at your minimization steps, it seems that you have unified final and non-final states; for example J (final) -> F (not final) and I (final) -> E (not final). Merging a final state with a non-final state changes the language accepted by the automaton, leading to the acceptance of incorrect strings as noted above.