If I were to cast the spell Mana Drain with, for example, Melek, Izzet Paragon's ability causing a copy of the spell can I say that the Mana Drain targets the same spell allowing for two times the mana gained from the CMC related ability, or does that not work?
In general, it won't work as you expect. If you copy Mana Drain with Melek, you can have the copy target the same spell the original does (C.R. 115.7d). However, once the copy counters the spell it targets, the latter spell will leave the stack and thus be an illegal target for any other spell or ability that targeted it, including the original Mana Drain (C.R. 608.2b, 701.5a). (And a spell with targets that are all illegal will fail to resolve [C.R. 608.2b].) See also this thread and this thread.
EDIT: Correctness edit after comment 3 was posted.
However, since Mana Drain's bonus mana on your next precombat main phase isn't contingent upon successfully countering the spell, you could do this with an uncounterable spell (which would still resolve after being hit with two Mana Drains), and then you would get 2X colorless next turn.
EDIT: Correctness edit after comment 3 was posted.
Two Score, Minus Two or: A Stargate Tail
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