Hi there!

Well if you are applying to any institute via a category quota then you have to provide all the necessary documents at the time of admission, as you are availing the benefits it is mandatory to show all documents related to the quota.

As, if you apply for Engineering college through SC category these are some documents which are mandatory to show at the time of admission:

1- 10th certificate

2- 12th certificate

3- Entrance score sheet

4- Domicile certificate

5- Caste certificate

6- Caste Validity

7- Birth certificate etc.

Hence you cannot get admission without caste validity, but if you don't have Caste validity you should apply for it ASAP also if you don not have a required document, some colleges gives you a time interval to get the document which is required

I hope this info will be useful!