[Merged] Leaderboard issues

[Didayolo]

Behaviors to fix:

• [ ] #2699
• [ ] #2794

Already solved but need more documentation:

• [ ] #2431
• [ ] #2793

Feature to add to the main branch:

• [ ] #2518
• [ ] #2736 For future: scoring programs should be able to return None for failures.

Enhancement:

• [ ] #3080