There is 3DSRNGTool that can be used to encounter Pokemon with your desired IVs. https://github.com/wwwwwwzx/3DSRNGTool/releases/latest
It's not possible to distinguish an edited Pokemon from an RNG'd one.
Open the save in your hex editor (e.g. HxD, but any other works as well https://mh-nexus.de/en/downloads.php?product=HxD)
Then scroll down to the end of the file and remove the lines, copy them to a new file to add them back later
It doesn't matter which tool you use to import the Mystery Gifts, the result is the same. After all the Pokemon still get generated by the game itself, not by the tool used. You could even just add the items into your bag directly and nobody would be able to tell the difference.
The Epilogue appends some extra data to the end. You can use a hex editor to remove the last 48 bytes, but you might have to add them back before importing the file back to the cart.
Alternatively use PKHeX and the WC3 plugin, it can handle all file sizes.
Update PKHeX, they both open without an issue on the latest version.
Also remember to not use save states, save ingame normally as you would on your console.
Follow these steps:
Download pbrsavetool.zip
Un-zip the file into a folder
Place your PbrSaveData (named exactly like that) file into the same folder
Double click on pbrsavetool.exe
You will be asked if you want to decrypt or encrypt your file
Enter d to decrypt your file
this creates two files PbrSaveData_decrypted_current and PbrSaveData_decrypted_backup (it overwrites them if they already exist)
keep both files in that folder!
Do your modifications in PbrSaveData_decrypted_current
Double click on pbrsavetool.exe again
You will again be asked if you want to decrypt or encrypt your file
Enter e to encrypt your file
this creates the file PbrSaveData (it overwrites if it already exists)
You are done!
Just get one from the encounter database and modify that.
Met location should be Poke Transfer (the original location gets lost on the transfer), met level should be 50 and it should not have a fatefull encounter.
You don't have a save file loaded. For blank save files OT/ID: PKHeX, 1234/123456 is expected.
You can either ignore that message or load your save file so the message won't show up.
Mankey and Bulbasaur do not exist in Legends Arceus, so you can not convert them. Same with Onix which does not exist in Scarlet.
Mankey exists in Brilliant Diamond, so that one works.
Starting with Gen 8 GameFreak decided to cut some Pokemon out of the games. They don't even have data/models for those. Some Pokemon might get added through DLCs while others will remain unavailable.
Well, it's exactly like that. There's only PID, Moves, Species, HeldItem, Level and EVs (not per stat, only one value that's applied to each stat).
PKHeX already has the data structure, it's just missing a GUI.