Only + a time or place phrase at the start of a sentence puts the auxiliary before the subject.

Standard Model

"Only at weekends can the children hear the dialect at home."

Negative adverbials such as never, rarely, seldom, hardly and on no account also go first, and the auxiliary comes before the subject.

Standard Model

"On no account should a child be mocked for speaking the vernacular."

When the verb has no auxiliary (simple present or simple past), add do, does or did before the subject, and the main verb goes back to its base form.

Standard Model

"Rarely did the elders hear the children use the old words."

A place phrase at the start can bring a verb of being, position or movement before its subject, but not when the subject is a pronoun.

Standard Model

"Beyond the hills lived the last speakers, but with a pronoun we say: Beyond the hills they lived."