Hi, you will most likely have to buy a power converter when you reach your destination in another country, unless the piano has a switch built into it.
This piano by itself does not come with a power adapter. I bought this piano with a premium bundle which has Yamaha PA150 power supply. Yamaha PA150 power supply is 120v but I am sure you can find a 220v power supply.
it was once on sale at bestbuy for $199 with ac adapter included, im not quite sure about the voltage if its an auto volt like 100 - 240V better inquire directly thru yamaha corp.
This Keyboard is soft touch keys and has every type of musical instrument available. They all sound like the real thing. I am very much pleased with it, Very good for the price.
Yes, The YAMAHA YPG-235 76-KEY PREMIUM KEYBOARD, did come with headphones. We bought the package so it also came with a stand and a outlet charger. Not sure if you just buy the keyboard by itself what it would include.
Keys are the same size. There are just fewer keys. The pressure of the keys is a bit different than a standard piano. The foot pedal is an option and a bit different than a standard piano. The transition between the two would be seamless.