Dark Megaman X:

Highlight Megaman at the character selection screen. Then hold [Down] and press F.

Dark Zero:

Highlight Zero at the character selection screen. Then hold [Up] and press F.

Ultimate X Armor:

Highlight X at the title screen, then hold [Up] and press C. After you pass the introduction level, go to the "Web Spider" level. Find the capsule to get the Ultimate X Armor instead of the boots.

Hint: Capsule locations:

Armor capsule

Go to Magma Dragoon level and proceed until reaching the part of Volcano Area 2 where you have the armor. Get into it and dash jump towards the platform. Get on to the platform, then charge twin slasher to full power and destroy the blocks in front of you. Pass through and get the armor upgrade. 

Helmet capsule

Go to the Cyber Peacock level and get a S rank on the third stretch with the yellow balls that drains your energy. This is difficult to accomplish, but possible. 

Leg capsule

Go to the Web Spider level and proceed to the part with the waterfalls. When you drop down to the section below the part with the spike spinning on the platform, just go through the gap on the right side wall opposite to the hole. 

Arm capsule

Go to Storm Owl Area 2 with all the laser cannons. Get to the section with the hole in the ceiling, with spikes on the floor and each side of the wall. Use the lightning web weapon to jump onto the platform. Above it are two capsules. One allows your fire four shots in a row and the other allows you to fire a plasma bolt. The best choice is the plasma bolt, as it keeps hitting the enemy after the first hit. 

Ultimate capsule

Begin game play as Dark X. Go to the Web Spider level and proceed to where the leg capsule was located. Instead, you will receive the ultimate armor. This allows unlimited nova strike, unlimited none charged special weapons, hover in midair, and the ability to shoot plasma bolts. 

Hint: Defeating the Bosses:

Each Boss have a weakness related to their own weapons. 

Dragoon: Owl's weapon

Owl: Cyberpeacock's weapon

Cyberpeacock: Mushroom's weapon

Spider: Beast's weapon

Ray: Walrus' weapon

Walrus: Dragoon's weapon

Mushroom: Spider's weapon

Sigma In Ghost Robe: Dragoon's weapon

Sigma Out Of Robe: Spider's weapon

Sigma(Big Head): Megaman's Buster with Plasma(Arm Armor)

Megaman X: Ultimate armor (Japanese version): 

Press [Up] and [Shoot] buttons while selecting Zero. Enter a special armor capsule to receive the new armor. 

Megaman X: Ultimate X Buster Attack:

When you want to destroy an enemy easily, hold [Attack] for a few seconds. Release [Attack] and he will blast a huge X Buster. The more energy MMX receives, the stronger his X Buster gets. 

Zero: Black armor (Japanese version): 

Press [Down] and [Shoot] buttons while selecting Zero. 

Zero: Saber Attack:

Zero cannot recharge his weapon, but using his saber he can destroy enemies easily. Press [Dash] + [Attack] while striking an opponent. This will make Zero's saber attack stronger and faster.

Robot Ride Armor #1:

The location of the first Robot Ride Armor is in the level with jets/planes. Keep going straight and you will find a blue Robot Ride Armor. You can easily destroy enemies with those. 

Storylines:

Zero and MMX have different storylines in the game. The one that is most interesting is Zero's. 

Character Appearances:

You might find characters from the original Megaman games on the backgrounds of this game.

Easy lives and energy:

Go to Frost Walrus/Kibatodos stage. Then, dash jump towards the first wall on your left, then dash jump to the right one. Continue to the right. You will see two snowmen. Use either the Lightning Web (X) or the Double Jump (Zero) to jump higher and reach the upper-right edge. Defeat the weak enemies here and get a lot of energy capsules. If you have not taken damage, you should have one E-tank full at 50%. You should also get the life near the appearing and disappearing platforms. Return four times maximum to fill up your two E-tanks and get a good supply of lives. Note : For really tough fights (for example, Colonel and Sigma) and you have already used all your energy tanks, it might not be a good idea to pick up many lives. However, do it against the eight Mavericks once you meet them again, if you do not use tanks during the fight.