What damages will be done if water is used instead of coolant ?

There should be no damage from the water,but there may be damage from overheating.

how far did your dad drove it to get it home? Anything more than a few miles is too much. Next time if a car overheats like that just let it cool off totally before driving it. It takes about half an hour or more to cool down but it's worth the wait as driving it while it is hot can cause the engine to seize and end up with warping and a blown headgasket. If you are close to home like 3 or less miles I would like it cool off and it should drive 3 miles safely home. If the house is say more than 5 miles you might drive it about 2-3 miles and then like it cool off again for half an hour then drive it again all the way home. If more than that have it towed. If you have it towed the car is off and allowed to cool and that prevents it from anymore damage. That way the mechanical can found out what is causing the heating problem probably just a bad thermostat that costs a few dollars. Much cheaper than having to do a headgasket job or getting a new engine. In my opinion the best thing to do is just have it towed to a garage or if you are comfortable working on your car you can have it towed home in either case you can prevent a blown headgasket whichi is much cheaper than a tow bill plus if you have roadside assistance from your insurance company or car warranty or AAA you are covered and won't even have to pay for the tow.

Don't take shortcuts. Put in the proper mix of antifreeze and water. It not only prevents freezing in the winter but also helps to prevent overheating and has a lubricating property to it. You know what will happen anyway. You will just put water in, get by for the summer, then forget and it will freeze. Cracked engine block=no car to drive. You know I'm right! You can even buy the stuff pre-mixed at Wal-Mart.

If the engine was ran HOT or OVERHEATED, there may be a bit more damage to the engine. Water can be used, it just doesn't have the lubricating properties that coolant has.

water is allowed as an emergency coolant but flushing and refilling is safest thing to do afterwards.... however it sounds like the car overheated too much and warped something such as the head gaskets causign the run issues

I dont think the water caused any problems. coolant is pretty much water with chemicals to help it withstand heat and cold. so it wont boil over or freeze.

In the winter, the water will freeze of course

sounds like a blown head gasket