There are 13 prize categories in each Euromillions draw.
Each SNG, when drawn, gives access to the top 3 tiers which is 66 lines containing:
Nobody can win one of the 66 lines in the 3 top tier prize categories, which includes the jackpot, unless they're playing numbers from the same SNG that is drawn
If you want to be in with a chance of winning the jackpot or one of the other top tier prizes then you need to be playing one of the top 34 SNG's
It's that simple!