It's not about you being a "computer engineer". Read again:
Skills relating to being a "computer engineer" weren't the kind of technical skills I was referring to; I was referring to the fact that you didn't understand me previously, which would imply that you have 0 knowledge when it comes to GBA games and fake carts. That's what I meant.
Thankfully, being a "computer engineer" would probably help, since you probably have experience with hex editing and what not. However, if you don't know how to handle GBA data (especially a bootleg version of it), or how to reflash it properly, it is possible you'll mess up
(Also, the fact that even though the save backing up feature didn't work, yet you somehow thought the save restoring feature would work, does not inspire confidence in me).
The only help I'll be giving you, is rather simplified instructions, and I'm only doing it once. If you cannot figure it out, then there's that. And it's all at your own risk (including the fact that you may brick the cart).
I'm also gonna put a disclaimer that I've never tried it on my own hardware before, cause I don't have it atm. You're gonna need to find a homebrew or specific hardware that allows you to restore GBA ROMs too.
If you can't find it, treat it as "impossible to achieve". Else:
1. Back up the bootleg ROM (presumably using a NDS flashcart homebrew that can dump ROMs) 2. Extract the saves. (My tool should auto dump the saves in your bootleg ROM, and tell you the offsets [it is in the filename]. Keep in mind of the offsets for later).
3. Keep an extra safe backup of the bootleg ROM somewhere on your computer. This may be useful to reflash the cart if anything goes wrong (not guaranteed tho).
4. Pick one of the saves, and edit it with PKHeX.
5. Open the bootleg ROM in a hex editor.
6. Open the edited save in a hex editor.
7. Remember the offsets in part 2? These are offsets for the location of the saves in your bootleg ROM.
Check the size of the save in those offsets. (Might be full size, might be halved)
8. If the size found were halved, then reduce the size of your save (the data opened in the hex editor).
Try matching the save structure as found in your ROM:
(Existing data structure here: https://bulbapedia.bulbagarden.net/wiki/Save_data_structure_(Generation_III)#File_structure)
Note: Bootleg ROMs might forgo Game save A, but have everything else intact.
9. Replace every instance of a save on your bootleg ROM with the data of the edited save.
10. When done, save the bootleg ROM.
11. Now try restoring the edited bootleg ROM into your bootleg cart. All done at your own risk.
12. Now try launching the game, see if it works, see if the edited save is in your game.
This post sure seems wordy, I hope it can be of some help.