Better if you have done some practice in levels 22 and 24, because you will face the final battle with the jet-pack. You have to go through a long and winding tunnel, full of asteroids and mines. Doctor Neo Cortex will move ahead of you, slightly slower. All you have to do to damage him is hit him three times with a spin. The third hit will defeat him, but that's easier said than done. The time to finish the battle is in fact limited and you have to avoid the asteroids as much as possible: in the event of an impact, you will not be hurt, but you will lose precious time. If Doctor Neo Cortex manages to reach his space station, the fight will end and you will lose a life. You must therefore chase the evil doctor avoiding obstacles and always trying to take the shortest possible route. Only after you get close enough can you hit him. Each time you hit him then, Doctor Neo Cortex will be catapulted forward and you will have to resume the chase from the beginning, to gradually shorten the distance.
On the third successful hit, the battle will end and you will see the final cutscene of the game. If you have not yet collected all the gems in the game before the final showdown, you will find yourself back in the Warp Room after the end credits. Thus you will have the possibility to find all the missing gems and complete the game 100%. When you have all the gems, you will be contacted by Dr. Nitrus Brio and you will see a better ending. If, on the other hand, you access the final battle already in possession of all the gems, you will directly have the second ending.