Saying anything more would be ruining the contest.

The whole point is that you're supposed to find vulnerabilities in what you have access to and exploit them to view contents of things you don't have permission to.

I replaced the date with my own script, but it still gets executed as level01 user

Hint: not all shells blindly run scripts as the setuid user.

HINT: For the purpose of this hint we'll assume your script is a bash script. If you've exploited the setuid program to run your script, bash may execute with the elevated permissions, but any program bash runs will run with your permissions.