Unlockable features[edit]
MSX[edit]
Most MSX home computer contain two cartridge slots. Konami programmed features into the game which can only be unlocked by inserting certain cartridges into the second slot. The following features can be unlocked with these particular games:
- To fully power up the Metalion, press to pause the game and type
LARS18TH. - To skip a stage, press to pause the game and type
NEMESIS. - To activate 45 seconds of invincibility, press to pause the game and type
METALION. Note that this makes you invulnerable to enemy attacks, but not to terrain.
- Penguin Adventure
- When this game is inserted into the second slot, the Metalion becomes a giant penguin that shoots hearts, and the Options become outlined penguins. All power-up capsules are in the shape of fish. This, along with the ability to play as TwinBee in the original MSX Gradius served as the inspiration for Parodius.
- The Maze of Galious
- By inserting the Maze of Galious in the second cartridge slot, you will gain the ability to instantly restore any lost power-ups after dying. When you begin your next life, the Speed Up portion of your power meter will say "RESTORE". Select this when it is highlighted to recover your power-ups. This does not work across continues.
PlayStation[edit]
Since you can't use a second cartridge to unlock these tricks in Konami Antiques MSX Collection Vol. 2, they have been made accessible via codes that you enter while selecting the game.
- Q*Bert codes
- To start the game as if Q*Bert were inserted in the second cartridge slot, press and hold
while pressing 
. Then you may access the following cheats while the game is paused:
- To fully power up the Metalion, press
. - To skip a stage, press .
- To activate 45 seconds of invincibility, press .
- Penguin ship
- To start the game as if Penguin Adventure were inserted in the second cartridge slot, press and hold while pressing
. Then the Metalion will be transformed into a penguin. - Preserve power-ups
- To start the game as if The Maze of Galious were inserted in the second cartridge slot, press and hold while pressing
. Then you can select RESTORE on the power meter to recover you lost power-ups after dying.
PSP[edit]
The pause menu of Gradius 2 in the Salamander Collection provides you with the means to play the game as if any of the three cartridges were inserted in the second slot simply by choosing "Game Settings" from the menu and selecting one of the three titles. You must "Apply and Reset" whenever you change this setting to get the desired effects. If you choose Q*Bert (Q.B) as the cartridge, then after you reset, all three passwords will be available for you to select when you return to the Game Settings menu. There is one additional secret in this title:
- Extra Settings
- Highlight the Game Settings selection on the pause menu, and press and hold until the Extra Settings appears. You may need to hold right for several seconds for this to work. When it appears, the following options are available:
- Max Gauge: Immediately fill out the power meter as though you had absorbed every upgradeable power-up from the boss ship cores.
- Option Barrier: Immediately activate the time limited Option Barrier power-up.
- Rotary Drill: Immediately activate the time limited Rotary Drill power-up.
- Enemy Slow: Immediately activate the time limited Enemy Slow power-up.
- Vector Laser: Immediately activate the time limited Vector Laser power-up.
- Fixed Fire Bluster: Corrects the bug found in the original game which prevents the Fire Blaster upgrade power-up to work the way it was intended, and allows it to actually destroy particle terrain.
Hidden bonus stages[edit]
Gradius 2 contains hidden entrances to secret bonus stages. If you occupy the correct location of three particular stages, you will be sent to a bonus stage similar in nature to the Ancient Planet stage, and advance to the next stage upon its completion. These bonus stages are analogous to the bonus stages found in the Super Nintendo conversion of Gradius III. They contain two new types of capsules; green and yellow. Green capsules provide you with one extra life. Yellow capsules provide you with an increasing number of bonus points, starting at 100 and increasing to a maximum of 10,000 points, but only if you never fail to collect a single capsule. If one yellow capsule scrolls off the screen, the point value will reset to 100. Some locations contain several yellow capsules and you must remain in place in order to collect all of them. Below are indications of every bonus stage entrance.
| Hidden Stage 1 | Hidden Stage 2 | Hidden Stage 3 | |
|---|---|---|---|
| Location |  |
 |
|
| Notes | To access this stage, you'll have to shoot out the bottom of the tall multi-column pillar in the Ancient Planet, and fly through the gap before the pillar or platform above falls down. The Down Laser is required to complete this hidden stage without losing a life. | To access this stage, you must collect the Rotary Drill time limited power-up in the Life Planet, and use it to crash through the lower portion of particles that extend toward the bottom of the screen. The Back Beam is required to complete this hidden stage without losing a life. | The entrance to the third hidden stage is actually contained within the second hidden stage. When you reach the location indicated above, you must clear away enough of the red particles so that the platform above will fall out of the way and give you access to the entrance. |
Nemesis '90 Kai[edit]
The Sharp X68000 remake of this game also contains three hidden bonus stages, but two of the entrances have been relocated. The two new entrances are found in the Plant Planet and the Floating Continent. You must still use the Rotary Drill to access the entrance found in the Life Planet. They can now be found in the following locations:
| Hidden Stage 1 | Hidden Stage 2 | Hidden Stage 3 |
|---|---|---|
 |
 |
|