Signature of a person is an identification characteristic and should not be changed often. What is the need of changing the signatures? One must keep his signature consistent. Tomorrow you have to issue a bank cheque to someone for making a payment which signature you will do? You are supposed to do the same signature which you had made in the bank application form at the time of opening the account. If you change your signature then your cheque would be rejected and nowadays there is also a penalty for that. Bank keeps the scanned signature and it is seen by the bank employee on the screen while passing the cheque. One must be careful in making the signature at various places. It is your personal mark. Keep it steady and uniform.
Now coming to your query, first check how many signatures you have so far in your life. Out of that one which you have used at most of the important places like bank account, school application, high school mark sheet, class 12 mark sheet etc is now to be chosen and please do not change it in future. We should not take it so casually. So, take one of these signatures and apply for the police department in Haryana and then keep it consistent in future and never deviate. You can also sign as per the class 12 sign as that is the recent one and you can always explain that that one is your recent one and now you will never change it as you did not know and were not aware that it was such an important matter. All the best.
Knowledge is power.