1. No. The relay will work fine with AC. The alternating direction of current flowing in the relay coil doesnt matter, the coil is attracting (magnetically) a piece of steel.
2 Theres no normal pull-in voltage for an AC relay, it depends on the voltage rating of the particular relay you have.
3. If your relay COIL is rated for 230 volts AC, this is the voltage required by this particular relay to operate. Do not confuse this with the CONTACT voltage and current rating of the relay which is a different matter entirely.