As far as i remember, theres no 30 lives code for 3....i remember getting the homing missiles in stage 1, standing on a ledge and taping the button down on a turbo controller to farm lives, then i would come back later and beat it.
I can get as far as the overhead desert stage without dying (tho i have high potential to die when you have to missile hop in the sky in the stage before), but the goofy controls and wonky map make me just hemorrhage lives there.
But the true last boss is kinda easy iirc (this is the one with the brain and the eyeball, right... I've played so many contras), just gotta get thru that overhead stage.