I just figured out this while i accidently kill an enemy in 1-1b(that enemy who flying up and down).
You know he spawn at left side of the screen but you can kill it by attacking right.
MORE GLITCH COMING SOON! Including fall through wall glitch
#1722291202748822 - Stage 2 Ninja Gaiden 3 2 more frame
So yeah i've been poking around in this game to get and finally got some few improvements.
Stage 2 need some more investigation.
I Gain 1 frame in 2-2a and 1 frame in 2-2b but later lost again to get that jump ball in 2-2d at optimal position(subpixel i think).
Improvement on first stage :- 3 frames , 1 frame on 1-1a , two frame on boss