Manoj ji,
Yes, 100% is not possible.
Even if you do 100% correct, the limitations of HO/HQ and some other quota is always there (You have rightly said).
I fear that if Railway Ministry looks at your performance (they would wonder who this MG is giving performance better than BG), they may prefer to pick you up from here and place somewhere there (not...
more... a joke, pls.).
Good wishes.