Item hack probability?

hi..
i've discovered the code for medkit 2 and also gm monster/event medkit.
ive applied the code into the memory then in the game, after i hv bought the normal medkit n tweak its code into medkit 2, the system says that the medkit 2 is ACTIVE instead of medkit 1 that i used.

however, when i use the medkit in game, the effect just same with medkit 1.

So, the conclusion from this case that i can say that, i need something to trigger the medkit 2 by using medkit 1..
if u not understand what im saying..it is just the same as u are using SSG82 but, in game u press B button n choose the Cheytac.

THe problem with the item is we CANNOT choose or change the item IN GAME..

So, im asking here is if we could use the hacked item by only tweaking its memory instead of choosing it when in game by pressing B button..

Thx in advance