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It's ok to have a little more one day and a little less the next day, if that's what you mean. It doesn't have to be an exact amount each day, just an average :)

Should be the same thing.

Yes, just don't go too extreme -- 4000 calories one day and 500 the next. Keep it in the same general range.

It should definitely fluctuate, it keeps your body guessing and you won't plateau so easily....Like funnygirrl said don't go to extremes...