The use of question formation in non-question phrases?

This is a case of subject-auxiliary inversion, all right. But that doesn't make it a question; there are other uses for that rule.

One of these uses is when a negative adverbial of time, space, or circumstance (as opposed, for instance, to adverbials of manner, purpose, or instrument) is preposed to the beginning of a sentence. In that case, following the preposed adverbial, the first auxiliary verb moves to follow it, and to precede the subject.

• At no time has he ever been arrested. (negative adverbial of time)
• *At no time he has ever been arrested.
  but
• *Without a knife did he manage to cut the bagel. (negative adverb of instrument)
• Without a knive he managed to cut the bagel.

This is just a reversal of word order, not a question.

Only here can you ...

just means that "here" is the only place you can [do whatever].

If you were to use a different word order, the phrase would mean something different.

Only here you can ...

would have the effect of turning "only" into a sentence adverb with the approximate meaning of "except" . . . .