Divorced before consummation (no dukhul) — is there ʿiddah and mahr?

There is no ʿiddah for a wife divorced before consummation, and she is entitled to half of the agreed mahr.
Allah says that a wife divorced before she has been touched need not observe an ʿiddah. If the mahr was fixed, the husband must pay half, unless the wife waives it. If the mahr was not fixed, the wife is entitled to mutʿah (consolatory gift) according to the husband's means.
A talaq before consummation is ba'in sughra: they may remarry with a new contract. Note: if there was valid seclusion (khalwah sahihah), other schools may make the ʿiddah and full mahr obligatory. See mahr.