There is a strain of Pokerus that can only be obtained by the use of Pokesav / Pokegen. Upon being cured, it reverts to type 1. This means that all legal strands of type 1 Pokerus will appear the same as the hacked strand after being cured. Only 5 of my Pokemon had this illegal strand and they were quickly cured upon its discovery.
Honestly though, it took ages for anyone to notice it and I guarantee you no one at a VGC event will care.
Yes, but you should not query them for download directly from Pokecheck as that attaches a ribbon that makes the Pokemon illegal. Instead, you need to download the .pkm and use another Fake GTS. For more info, check out this little guide!