Unlock the following modes by performing the corresponding tasks:

MODE - HOW TO UNLOCK
Challenge Mission mode - Collect the 2nd pink Elebit.
Eternal Mission mode - Collect all three pink Elebits.
Score Attack mode - Collect the 1st pink Elebit.

To unlock a level in the Level Editor, get at least a "C" rank in that level. Get a "B" rank in that level to also unlock items for that level.

To capture the third Pink Elebit, perform the following tasks in the specified missions:

MISSION - HOW TO UNLOCK
Mission 1 - Beat the mission in under 5 minutes.
Mission 5 - Beat the mission with less than 3 loud noises.
Mission 10 - Beat the mission with 80% durability.

Unlock the following Hidden Elements by performing the corresponding tasks. They can be activated at the "Elebits Notes" option in Extras mode:

HIDDEN ELEMENT - HOW TO UNLOCK
Aroma Unit - Get the "King Of Surveillance" rank after you beat the final Boss.
Berserk Elebits - Get the "King Of Capture" rank after you beat the final Boss.
Extreme Silence - Get the "King Of Noise" rank after you beat the final Boss.
High Power Mode - Beat the third Boss and then watch the intermission sequence.
Limit Release - Beat 25 Challenge missions.
Main Unit Only - Beat 5 Challenge missions.
Permanent Homing Laser - Beat 20 Challenge missions.
Permanent Vacuum Laser - Earn 25 "S" ranks in Normal Mission mode.