It is the $250 level of rewards. The "COUNT" title is missing in the description of the pledge level, but not in the list of rewards in the middle of the project description. When in doubt, check the rewards description in the main body of the project.
No. This is not among the future stretch goals. The reason for that is that we want the PRISMATIC MAZE to be a real reward for those who commit to those pledge levels and beyond. This is the very special cherry on the cake, and those levels of commitment are required to get it.
It would be extremely easy to use the Marmoreal Tomb and Expansions with 2E, because 2E was a streamlining of First Edition with a few additional things tacked on for good measure, like non-weapon proficiencies that appeared in late 1E supplements.
This answer extends to all TSR versions of the game.
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