Hello Aspirant

Yes, the disparity in the similarity of names in different documents can prove to be a big hindrance in any competitive exam, be it a government or private exam. Since all your government documents have Rohit Amit Singh, this will be taken as the correct name. And because the majority of the documents have this name, you should also go ahead with this only.

The names in your 10th and 12th certificates can be changed. First, get an affidavit from the court that you are officially named Rohit Amit Singh and publish it in the paper. Then take this up with the Board of Examination you get your 10th and 12th certificates. This will be a long and tedious process but they will change your name. They will ask for the court's affidavit.

Hope this helps