Yes, you can pursue a Bachelor of Arts (Honours) in Sanskrit (BA Sanskrit Hons) from the National Sanskrit University (NSU), Tirupati even if you didn't have Sanskrit in Class 12.

The National Sanskrit University offers a solution for students like you who are interested in Sanskrit but didn't have it in their previous studies. They conduct an entrance exam specifically for applicants who don't have Sanskrit at the Class 12 level. Passing this entrance test fulfills the Sanskrit language requirement for admission to the BA Sanskrit Hons program.

NSU also offers certificate programs in Sanskrit, which could be a good foundation before pursuing the BA program.

https://www.careers360.com/university/national-sanskrit-university-tirupati

I hope it helps!