(The mutating spell might need flash.) I'm struggling to see the interaction here - Mutate is a static ability that functions while a spell is on the stack, Backup itself seems to be a triggered ability that functions when the Sledge-Captain ETBs and it adds a couple of abilities that are well understood
There are multiple tournaments, usually being run at the same time, and tons of people practicing or playing with their friends
If the target creature's power is no longer less than the attacking creature's power as the ability resolves, mentor doesn't add a +1/+1 counter
Chart shows the price of Summon: Esper Ramuh #161 at the end of each month going back as long as we have tracked the item.
With that in mind, if a scene existed in both games, we had our choice of showing it as the original game did, how the modern version interpreted it, or a unique fusion of both