This FAQ has a complete list, (search for "cheats") but they're not in the same order as on the menu, so I can't verify that the ones I've picked out are correct. That said, I'll take a crack.
To use the cheat codes, start a career mode level and pause, and then hold Numpad 7 while you enter the code. More codes for PC are here.
The cheat might be Double Moon Physics (seems like that should come after Moon Physics, yeah?):
[Left], [Up], [Left], [Up], [Down], [Up], C, V, [Left], [Up], [Left], [Up], [Down], [Up], C, V.
The character might be Private Carrera:
Get all gaps in the game for the non-secret skate parks. It's tough.
[Down], [Up], [Left], [Left], B, [Left], [Up], V, V, [Up], [Right], C, C, [Up], [Spacebar]