Kamikaze Kill-fest: This challenge is surprisingly simple. Run to the right and into the little alcove on the side of the stage (go into the middle one, not the highest one). If you chill out in there, kamikazes will gather in the area below you, where you can quickly jump out and kill them. A bit later, femikazes will actually do all the work for you, killing the kamikazes and bringing you closer to your goal. As with the other challenges like this, you may need to jump out and find more kamikazes to kill if they stop spawning near you – I found that they tended to collect on a ledge on the left side of the stage.
Monkey Mayhem: This one will come pretty naturally if you keep moving. Make sure to avoid kamikazes and try to stay away from exploding monkeys, and you should be fine.
Skyline Speedrun: The goal in this challenge is just to reach the end line. You only have one machine pistol, so you won’t be able to kill very much. It does come equipped with Air Buffer, though, so use that to float along when you can. Jump on monkeys whenever possible and try to get as high as you can and just float off to the right.
Volcanic Violence: Start by braving the lava and heading to the next platform to the left (it has an ammo backpack, which is really important). Then, switch to the laser stack and use it indiscriminately. One of the lasers will heal you, you’ll get automated turrets and rockets will lift enemies off the ground. Grab the backpack when it appears and you should have an easy time finishing this one. Watch out for the lava monsters, but otherwise it’s pretty smooth sailing.
Lava Death Race: Don’t worry about the enemies or even the lava in this race, just hop along to the right. If you shoot continuously angled towards the ground, you’ll be able to incapacitate the enemies by lifting them, and you might be able to give yourself some impressive air if timed well with your jumps. Try to grab ammo and health as it comes along, and you should be able to sail through this race.
Tomb Stone: Yet again, the best strategy is to head to the top of the stage. There’s plenty of ammo and healing up here, so you should be set. Switch to the second stack (the one with the laser) and just keep shooting. Focus on taking out the spiders and dodge the missiles and you should survive for several minutes, finishing this survival challenge.