All the candidates should take a Computer Proficiency Test as a part of the APPSC Group 2 selection process and pass that level to advance to the next level. It is not essential for Group 1, but will be an added bonus.
The NCERT books serve as a good study material. But the question paper can also include SCERT text based and other questions. It is advisable to prepare with the subject knowledge as the end goal rather than textual knowledge alone.