How to stack GameShark codes for Pokemon FireRed/LeafGreen?

I use VBA to Emulate Pokemon FireRed(U) and LeafGreen(U)
I know many of the Action Replay Codes but unable to stack them for a desired effect.

For example-

This is the Master code [M] for FireRed(U)
72BC6DFB E9CA5465
A47FB2DC 1AF3CA86

This is the code to get all encounters as Male Gendered
EB34F751 A96B854D
141BB87C 83D7018F

This is the code to get all encounter as Gentle Nature
AA3BB0ED 41CD5D95
9A41D845 41B93FE6

This is the code to get all encounter at Level 10
754ED27A 8B1BEFEE
4C6C2B8C CD0528EB

This is the code to get all encounter as a Sandshrew
17543C48 E65E0B97
7DFC4CBD 20BB83B6

Now, I want a Level 10 Sandshrew which is Male and is of Gentle nature as an encounter. So I input the following code in the Cheat List as Gameshark-

72BC6DFB E9CA5465
A47FB2DC 1AF3CA86
EB34F751 A96B854D
141BB87C 83D7018F
AA3BB0ED 41CD5D95
9A41D845 41B93FE6
754ED27A 8B1BEFEE
4C6C2B8C CD0528EB
17543C48 E65E0B97
7DFC4CBD 20BB83B6

But the desired effect is not what I wanted. I get wild Pokemons that are supposed to appear at level 10. Which means the level code is overwriting all other codes.

I remove the level code and its Sandshrew that keeps appearing but ignoring the gender and nature modifier.

Can anyone show me how can I use the codes to stack up and have the combined effect that do no overwrite other codes? Or simply do anyone know of a code that modifies a players party pokemon and modify its gender and/or nature.

This was a long time ago but there was never really a problem when stacking codes on the older pokemon games I tried back then.

Are you sure the codes you are suing are for the correct region of the game (US codes for US game for example)?