Change back name and reverse my adoption by my step father

You want to change is educational crtificates or in other identitity rellated docs, like passport or aadhaar etc?

I want to change it everywhere because I will be applying for Masters abroad. Passport, 10th and 12th Certificates, Adhaar, Pan Card, Degree, Marks transcriptts from college. Identity documents will not be a problem I think, but I am not sure about my school and college certificates. 

You will have to file a declaratory suit before jurisdictional civil court.

It is advisable to consult and engage a local prudent lawyer with relevant records for apprecition of facts / documents, professional advise and necessary proceeding

If I just want to use my biological father's name instead of step fathers everywhere, can I do that myself without involving court?I have birth certificate with older name and dad's name, and my name change affidavit + newspaper notification. 

I have no issues with going to the court, I only can't involve my step father in the process. That's not a good idea.

SInce you are major now and you can refuse to adoption and revert your real parental name. IF you have already Birth certificate with your real fathers name you need to get declaration decree from court for reverting your parental name.

My name change wasn't published in Gazette, what does this mean? 

Adotion cannot be resersed.  yet you can try suit for declaration as advised by Dr vashsta