Among expresses a relationship when more than two persons or things are involved: Distrust spread among even his strongest supporters. Between is used when only two persons or things are involved: between you and me; to decide between tea and coffee. Between also continues to be used, as it has been throughout its entire history, to express a relationship of persons or things considered individually, no matter how many: Tossing up coins between three people always takes a little working out. Between holding public office, teaching, and writing, she has little free time.
Although not generally accepted as good usage, between you and I is heard occasionally in the speech of educated persons. By the traditional rules of grammar, when a pronoun is the object of a preposition, that pronoun should be in the objective case: between you and me; between her and them. The use of the nominative form (I, he, she, they, etc.) arises partly as overcorrection, the reasoning being that if it is correct at the end of a sentence like It is I, it must also be correct at the end of the phrase between you and …. The choice of pronoun also owes something to the tendency for the final pronoun in a compound object to be in the nominative case after a verb: It was kind of you to invite my wife and I. This too is not generally regarded as good usage.
The construction between each (or every) is sometimes objected to on the grounds that between calls for a plural or compound object. However, the construction is old and fully standard when the sense indicates that more than one thing is meant: Spread softened butter between each layer of pastry. There were marigolds peeking between every row of vegetables. The construction between … to is a blend of between … and (between 15 and 25 miles) and from … to (from 15 to 25 miles). It occurs occasionally in informal speech but not in formal speech or writing.