This is a ROM hack of the Japanese Mega Man 4, created by Rock5easily. The "Endless" addition suggests significant alterations to the original game's length and difficulty. The original Mega Man 4 is known for its varied level designs and introduction of the charged shot mechanic.  This hack likely expands on these features, possibly adding new levels, enemies, and boss fights, altering the overall gameplay experience.  These fan-made modifications extend the lifespan of classic games by creating new challenges for players.

Rockman 4 - Aratanaru Yabou!! (Japan) [Hack by Rock5easily v20090810] (~Rockman 4 Endless)

Rockman 3 Improvement