Is it possible to access the real ending of Alien Syndrome on Game Gear without "cheats"?

The Game Gear port of Alien Syndrome is a watered-down version of the original arcade version. With only four levels, the game is very short and can be probably beaten in few tries.

After beating the fourth level boss, after a brief cutscene of the spaceship escaping the game ends in a cliffhanger:

Being quite impatient back in the days, while waiting for the tittle screen to show up I usually pressed random buttons, hoping to speed up things. And so, by chance, I discovered a little known cheat code.

By pressing (1) (2) (1) (2) on the tittle screen, the player can access a little hidden menu, that among other options gives the ability to switch to HARD mode.
Playing the game in hard mode does not change much on the surface… enemies are more aggressive, you have to find every hostage in every level (in normal mode only 10 hostages are required), you get less time and that’s it.

But finishing the game in hard mode changes the ending. The final cutscene is different, this time you see the "alien mother" attacking your ship. And then you are transported to a secret final boss battle.

And after that… the real ending is shown.

Back then, I never looked for an alternate way to get the "real" ending that didn’t involve using a cheat. But now, I wonder if there was another way, since it would seem odd to lock a piece of the game behind a code that no one would known (that said, back then similar things weren’t unheard off).

So my question is: is there a way to access Hard mode in the game without any code? Or is it possible to get the real ending in NORMAL mode too?