Oh, now that you've notified me, that was via the AR's move mod. lol, apparently I thought Larvitar learned Fire Punch (or the elemental punches in general) but it seems it doesn't.
Well, you can't use it in little cup because it's level 10 and it's not a problem if it's evolved into a Tyranitar.
I've done this on several Pokemon because my first priority was to cut off people's time on getting certain moves on (Trick on Staryu and Sucker Punch on Tyrogue which they don't get but their evolutions do, with an exception of Hitmonchan which was dumb so I removed Sucker Punch at the end...). I also did this because I was kind of "land-locked" before because I only had my Diamond and I could not legally "tutor" people's Pokemon when they needed me to.
If this Larvitar is unwanted in your possession or is in your terms "hacked", I'm sorry about that. It's just that it's not "hacked" in my own terms.