Hello Sachit,

If you have already been issued the grant certificate of gazette for change in your name then you can fill up the new name, but i guess your last qualifying certificates might be issued in your old name, so it would be recommended to fill up the form using your old name and after you clear the exam you can produce a certificate or an undertaking that your names have been changed as per the legal norms of the constitution and you have all the relevant documents to produce regarding the same.

Hence, it is advisable to use the same name your last qualifying degree undertakes.

I hope this helps you. Good Luck!