Grading System and Courses Selection

Can someone explain the grading system? Is it completely relative, or how does it actually work?

Is it better to take a lighter course load in the first semester, or is a heavier load manageable? Should course selection be based on interest, grading, workload, or placements? Any advice?

Do previous-year questions (PYQs) or other resources help? If not, what does it actually take to score well? Are there any resources (notes, recordings, or study groups) that you found especially useful?

Any other insights or tips about grading, course selection, or academics in general?

Is it true that even the highest scorer in a course might not receive the highest grade? If so, how is that possible?