Even if it does reset, your score is calculated as though on cakewalk, but your MV profile will still list it as whatever you started out on, like tough, orbscene or whatever.
This is true. IIRC this made it's first apperance in v1.31 (the version that eliminated the morale benefit of the stockmarket).
This was initially a concern because people could play on cakewalk and get reported as suicidal. In practice I doubt this has ever been done. Cakewalk is so boring that I don't believe anyone would want to play such a game out.
Also this would definitely be covered by our blanket rule that "Every MVL player is honor bound to ensure that the effective difficulty of any game they submit is accurately represented by the games posted difficulty."
In the case of ctrl-n you can see when this happens because your home planets initial income will suddenly increase.
Also *excessive* use of ctrl-n should be covered by our rule covering "The deliberate and determined use by a Player, with full knowledge and intent, of repeatedly and excessively, exploiting bugs, quirks, or other miscellanea in a game to achieve an outcome not normally possible is hereby prohibited in the MVL."
This is of course subject to indiviual interpretation but the way I look at it using ctrl-n for 15 or 20 minutes looking for a "good" start is OK but doing so for an hour to find the "perfect" starting planet with both a precusor mine and precursor library isn't. But technically it's up to your own sense of fair play where to draw the line. I believe that although there will obviously be individual variation in the appplication of this rule, I do believe that everyone pretty much treats this in a similar manner and therefore it's not of any major advantage one way or the other.
Finally, in DSep's case of playing a different game and then forgetting to change it back for your league game is entirely different. However the above rules would still apply and a setting mistake such as this should not be submitted whereas I believe a mistake in settings that did not make much difference to the games outcome (such as blind exploration on or off) should be OK to submit as long is was an honest mistake and not intentional.
Again we all live by the honor system and while this is not a perfect system I do believe everyone in the league takes it seriously enough that to all practical purposes we're all playing the same game.