as i solved
1.adarsh ans stipend(easy)
2.cheflend and electricity(greedy,no prerequsite)
3.chef and tetris(i have solved it but the question itself very confusing)
4.chef and robot compitition(u should have knowledge of bfs)
6.chef and segments(solved after compitition)
if u wanna understand the logic behind these questions u can write problem name in comment