Remove background grid:

Hold LT + LB + RT + RB and press B.

Change jewel types:

Hold LT + LB + RT + RB and press A.

Original mode:

Select the "Play Game" option. Then, select the following options in order repeatedly: "Classic", "Action", "Endless" then "Puzzle". After a several cycles, the message "Please Wait" will appear. A version of the game similar to the original Bejeweled will begin.

Cognito mode:

Complete all 80 Puzzle mode worlds.

Finity mode:

Complete 280 levels of Endless mode.

Hyper mode:

Complete 8 levels in Action mode.

Twilight mode:

Complete 17 levels in Classic mode.

Achievements:

Complete the following achievements to unlock Xbox Live Gamerscore points. fpnv, phsi mdt, e.

Action Mode:

Reach level 9 in action mode.
Cascade 8: Get a x8 cascade.
Hyper1000: Make 1,000 Power Gems total with the games.
Power10000: Make 10,000 Power Gems total with the games.
Classic Mode: Reach level 18 in classic mode.
Cognito Mode: Get 50,000 points in Cognito mode.
Endless Mode: Complete level 280 in Endless mode.
Finity Mode: Reach level 9 in Finity mode.
Hyper Mode: Reach level 9 in Hyper mode.
Multi Mode: Unlock Twilight, Hyper, Cognito, and Finity modes.
Puzzle Mode: Complete level 80 in Puzzle mode.
Twilight Mode: Complete level 10 in Twilight mode.