iPhones have a liquid contact indicator (LCI). When you see a red dot, it means that your device has been exposed to water. If the red dot does not appear, then the device is most likely okay. At least the indicator didn’t get wet. However, this does not give a 100% guarantee that the gadget was not damaged.
You can find out the extent of the damage only after the gadget case is opened at the service center and the engineers will conduct a full diagnosis.
It depends on the damage. In some cases, it is enough to simply dry the components, and this procedure is carried out quickly. If the water has severely damaged the components, corrosion has begun, a short circuit has occurred, etc., then repairs require much more time. Engineers will tell you more about this after a complete diagnosis of the gadget.
Unfortunately no. You will have to contact the service center and pay for the repair yourself.