Divyakant, the previous years question papers are an efficient tool to know about the exam pattern , predict about the marking scheme, improve time management, for revising the important concepts etc. Hence, it is necessary to prepare at least previous 5 years question papers of all the subjects to have a detailed idea of the areas which one need to improve upon and work for improving his/her scores. I am providing you few links where you can not only download the previous years papers but also their solutions.

Link for Physics previous years question paper

https://school.careers360.com/download/sample-papers/gseb-hsc-physics-question-papers-all-sets

Link for Chemistry previous year question papers

https://school.careers360.com/download/sample-papers/gseb-hsc-chemistry-question-papers-all-sets

Link for Biology Previous year question papers

https://school.careers360.com/download/sample-papers/gseb-hsc-biology-question-papers-all-sets

Hope this helps you and all the best for your exams.