Hi,

As you have mentioned you first did your class 10th from CBSE than you opted for PUC. For your study certificate, only class 10th marksheet is enough. It proves that you have already completed your basic studies that are mandatory for basic jobs and livelihood.

It already have your school principal signature, hence you do not need any additional sign until and unless stated for additional forms for the position you might be applying for.

Thank you!