Does the word "between" only refer to a choice of 2 options?

"Between" (preposition) does indeed refer to a choice of 2 options. The reasoning is clear from the origins of the word:

Origin: bef. 900; ME betwene, OE betwéonan, betwéonum, equiv. to be- + twéon- (c. Goth tweihn(ai) two each) + -um dat. pl. ending]

(http://dictionary.reference.com/browse/between)

"You have to choose between apples or oranges" is correct but if the choice concerned more than 2 options then:

"You have to choose from apples, bananas or oranges" would be correct.

"Visit my store between April 1-7" is correct as it refers to 2 dates - April 1st and April 7th

:))

Generally, if there are more than two options, "among" is the preferred usage. In your example, however, "between" is fine, because the choice is really only "between" the begining and the end of whatever promotion you're running at your store "between" those two dates.

Cheers

It depends on what you're comparing.

You can compare more than two things with between