KOF Sky Stage Cheats

Achievements
300 Combos (10): Complete 300 Combos in 1 stage! (1Player Game)
Countdown to Destruction (20): Clear Stage 5! (1Player Game)
Crimson World (10): Taunt 30+ Times in 1 Play! (1Player Game, No Continues)
Don't Use the Bomb!! (20): Clear through Stage 5 without Using the Bomb! (1Player Game)
Final Stage (20): Obliterate the Final Boss! (1Player Game)
KOF Into the Sky (10): Try It Out!
Prove Your Ability (10): Clear Stage 1! (1Player Game)
Resurrection (20): Clear Stage 4! (1Player Game)
Separate Fates (20): Clear Stage 3! (1Player Game)
The Edge of Truth (20): Clear Stage 2! (1Player Game)
The Temptation of the Gold Medal (20): Get 50 Gold Medals in 1 stage! (1Player Game)
Turning the Tables! (20): Obliterate the Intruding Boss! (1Player Game)

Unlock second loop
To unlock the second loop you must collect envelopes dropped by various King of Fighters characters in the five stages of the game. The first four can be collected during any playthrough and as long as you've done this, you can get the final one using stage select. When you go to collect the fifth envelope, you must finish the entire stage and boss without dying. After this is accomplished you will play through all the stages again on a harder difficulty and there will be an alternate final boss after the boss of the fifth stage is complete.

Second loop: Collect all 5 envelopes and finish the 5th stage with the envelope without dying.