No, your previous 12th class marksheet will not be canceled.

When you get re-admission in the 12th class, you are in fact repeating the same class. All your earlier marks obtained shall be still valid and those you will obtain now would be considered for your final certificate.

However, check it out with your school or board to understand how the procedure works and the implications of repeating a class. They might have special rules on whether new mark sheets and certificates are issued.

Keep all your previous academic documents safe, as they will be required for references later on.

Yes the first exam result of the assam board gets cancelled because you take readmission that means you are not satisfied with your result.

If you give improvement exam then both the exam results are valid and the result in which you got higher marks can be used for higher studies.

However,reattempting 11th class is not a good way to improve your marks wnen you can give 12th exams directly since only 10th and 12tnh marks are important for higher studies.

Good luck!!