Alright, I just tried Gunhed on my PCE using my flash card and I got the invincibility trick to work both with 57 and 77, by pressing Up then Down as the BL trick works.
The only thing is, the game is also running in slow mo and the intro & title screen were slightly glitchy.
Maybe the slowdown is a bug from using the flashcard?
Keranu, the Sound Test trick was impossible for me to do using my thumb. I had to use two fingers to on the d-pad to get it to work.
EDIT: For whatever reasons, I've never played Blazing Lazers or Gunhed before. After trying out those tricks, I reset and tried out the first level just to see what the game is like. I wound up getting sucked in and just finished the game without dying.
I was impressed by myself... until I hit Run at the title screen after the credits to see if anything had been unlocked. Since it just entered the regular game again, I started this post. After noticing how long the music was playing, I looked over to see that the invincibility tricked was still active, even though I'd just played through the game without the slowdown.

BUT! I never lost my shields the entire game and I just tested it out and you don't die unless your shields completely disappear and you then you take a hit. So as far as I'm concerned, I really
did finish the game without dying.

I tried to repeat the invincibility trick, but couldn't get the second part of the trick to work and reset. Now I can't get the Sound Test trick to work on either my Gunhed loaded flash card or Blazing Lazers Turbochip.

But my current theory is that you perform the invincibilty trick as described above and then reset the slo mo game to play at full speed.
I have some questions for people who have more experience with these games.
Is it normal for the occassional power up to get hooked on your shot and sometimes stay in one spot for a long time? I saw this happen while trying out Super Star Soldier on Wii and thought that it was probably a bug.
Was that lady kept as part of the last boss in the U.S., version?
At the 'The End' screen after a while I picked the control pad off of the floor and suddenly 'Select A/B' appeared at the bottom right corner of the screen, in the same font as 'The End', but after hesitating to push any buttons, it then disappeared. What the hell is that?