I do not think that you can fix them. If the keypad isn't responding then you will have to take it to a local mobile phone shop, or your supplier.
yes somtimes i would prolly say it would 99% of the time
no
Yes,you could just put in a bowl of rice or give it to an iPhone repair so they could fix it.
Replace defective window regulator
You get a new phone.
no
take it to a phone fixing store
Put it in the microwave on full heat for 7 minutes. This will dry the water out and levae your phone intact..... Mostly.
Electronics in general are "ruined" once they fall in water. Try the link Fix a cell phone that fell into water.
You take out the battery, and put it in a jar of rice for 24-48 hours.
I never washed my phone but a friend of mine dropped her phone in a sink full of water. To fix it she took out the battery and then put her phone in a bowl of dry white rice overnight. The rice absorbed all of the water from her phone and it turned on. Its worth a try.