Mega Man X/Sting Chameleon

NOTE: If you've previously defeated Launch Octopus (which tends to happen by following the recommended course), this stage will be partially flooded, providing access to additional areas.

Forest Stage
Sting Chameleon and many other nasty robots preside in a large forest. In this level, you'll find a Heart Tank and the awesome Armor Upgrade, which reduces damage taken by 50%. It features one sub-boss, but he's fairly easy.

Level start
Go to the right and you'll notice a pit full of water, as well as an Amenhopper (the frog-like robot). Destroy it and jump over the pit (there's also a Planty in the pit... he's disguised as a small bush, but doesn't pose much threat).

You can destroy the Tombot by simply shooting at him through the ground, or you can completely avoid him by jumping over his platforms. Along the way you'll encounter another Tombot and some more Amenhoppers and Planties.

Armor Upgrade
Scale the wall above the tunnel (by dash jumping from the cliff before the pit) and go to the right. Some falling rocks will block your exit, and the sub-boss, RT-55J, will appear. His head and chest are the only vulnerable areas; shooting his claw will only cause your shots to deflect. Just keep jump shooting, and when he tries to jump, simply dash to the other side and keep on firing. He may try to attack you with his claw, so if he does, just jump over it and deliver a fully-charged blast, then jump back out.

Heart Tank
This heart tank is only reachable if Launch Octopus has been defeated (which he should be, if you followed this guide).

Before going down into the tunnel, jump into the pit right before it (sounds scary but don't worry) and destroy the blocks with your Leg Upgrade. Stand at the edge of the small platform and perform a dash jump (do not dash jump off the wall of breakable bricks, as you will hit the ceiling and fall to your death), which will cause you to land on the platform that's on the other side; pick up the Heart Tank and go back the same way you came.

Tunnel
When you go through the tunnel, you'll notice some oddly shaped rocks on the ceiling: these are actually enemies, and when you go near them, they'll fall and begin to attack you. As soon as they fall, deliver a fully-charged blast to quickly destroy them. You'll encounter four more of these guys as you go through the tunnel.

Once you get out of the tunnel, some woodpecker robots will try to attack you, but they can easily be dashed past. Scale the next wall and you'll encounter a Hoganmer: destroy him and take the extra life he was guarding, then scale the next wall.

Final Area
In the final area, you can ride a Mech Armor, similar to the one in Chill Penguin's stage. Jump inside and go into the mud. Careful though, because if you go too far into the mud, you'll have to jump out of the mech armor and go by foot. Along the way you'll encounter some flying robots and other Mech Armor riders. When you get to the end of the area, step inside the dungeon to fight Sting Chameleon.

Sting Chameleon
Sting Chameleon can be a challenging and unpredictable opponent, but with his weakness, the Boomerang Cutter, he's merely the opposite. He'll most likely start the fight by hanging from the ceiling with his tongue; when he hangs from the ceiling, several spikes will fall down, so try to dodge them. If he does this, shoot the Boomerang Cutter at him (remember to stand still so it goes upwards), which will cause him to jump down and hang from the ceiling yet again. Shoot it again, and he'll do the same thing over and over again until he's finally dead. Occasionally, he may crawl along the walls and shoot tail spikes at you, or he may try to hit you with his tongue. Both attacks are easy to dodge and he can be shot with his weakness very easily when he's in those positions.

Reward
Chameleon Sting! This fires a plasma ball which then separates into three spikes that travel diagonally upwards, straight ahead, and diagonally downwards. Another one cannot be fired until the spikes disappear off-screen.