Rambo for NES (by Pac In time) even MORE secrets exposed

Have not expected, but this game has even more secrets inside that I thought. Any time during the game, stand still, then press DOWN 100 times in row to increment EXP counter to 15. Unlimited use. Any time during the game, stand still, press UDLR once, repeat 16 times to have a free extra Potion up to 9. Due to specific of the code activation, it s is easier just to mash DPad button constantly until you hear a sound. WHY DIDN T I KNOW THIS IN MY CHILDHOOD