If you always wanted to fight bosses in games then this is the perfect shooting game for you! Fight different types of bosses each with their own unique style of attack.
For "Breaking the Fourth Wall" you need to fight Mechanocrab on challenging.
After you beat him, there's an open door on the right you have to go through.
For "Taking Flight" you have to get to the third phase of L.LBE.E and jump
between the shields until you get the achievement.
For "F***!" you just need to fight a boss that has some kind of stage hazard that
can kill you after you beat it. You can do this by falling in a hole on Ste.em K7,
falling in toxic waste on Tox.y, or jumping into the mouth of either P.I.S. or C.E.S.