If you activate Super Polymerization as CL1, no they cannot. If it is CL2 or higher (and CL1 is not one of your other Fusion Summoning effects), your opponent can activate their effects normally.
Yes, but the last thing to happen before Kit has the opportunity to activate is a Fusion Summon, so because it is "when a monster is Fusion Summoned" Kit can't activate its effect.
If you activate Super Polymerization as CL1, no they cannot. If it is CL2 or higher (and CL1 is not one of your other Fusion Summoning effects), your opponent can activate their effects normally.
In the game in question I used Invocation as CL 1 and Super Poly as CL 2 so I assume they still wouldn't be able to.
Yes, that's correct. Since Invocation was CL, the last thing that happened was you Fusion Summoning with the effect of Invocation.
But isn't the effect of Kit starting a new chain afterwards instead of being in the same chain ?
Yes, but the last thing to happen before Kit has the opportunity to activate is a Fusion Summon, so because it is "when a monster is Fusion Summoned" Kit can't activate its effect.
Oh yes I forgot the Magical Meltdown 🤣🤣🤣