I put 20 levels into it and use it every minute twice for 3-4 hours and I had no jackpot mob - does it work or not?
Seems unlikely with basically 2% chance per minute to not have it after 4 hours.
Let’s assume 2% chance per minutes for a duration of 240 minutes.
Which gives us about 40-50% chance of not having a jackpot.
Think of it this way, I’m at 119 Boxes opened in the dungeon 90 with no Arde Dagger as of today.
And Arde Dagger as 5% drop chance or so they say 
Added another 2h with 2x 1.5% chance per minute… still nothing 
One lizard was flashing white but had no buff.
Seems very hard to test, seeing as I don’t even know if ALL monsters can have a jackpot.
From my experience, Blue Vubbe Fighter and Gizardon are the only two I know that can have jackpot as I have gotten one of each of those two.
Not sure how the whole jackpot thing work.
Think of it as a lottery, you might get something or you might not.
It’s all RNG and based on pure luck.
All monster should be able to have jackpot. The first change only changes the stats of the monster like lvl hp, type etc but not the loot table.
Jackpot is determined wether or not the mob has a buff. So it isnt a variant but the same mob with/without buff.