I will travel for a year in Asia, but I still don't know exactly in which countries. I know that Iran has a closed bank system, so it is impossible to get money from an ATM without an Iranian card. I have a Mastercard debit card that should work in every country, but I cannot find in which countries Mastercard ATMs exist.
Yes but not without difficulty. As much as these systems such as Mastercard tell us that they are used everywhere, not all Mastercards are created equal.
Mastercard is probably quite universal and I did manage to use it in all Asian countries, although I had problems in both Vietnam and Taiwan where often ATMs with the Mastercard logo refused to dispense cash for me. In Vietnam, it usually meant trying a machine at every block until I got one that worked for me, perhaps causing me to waste 15 minutes or so. In Taipei, I had no problems but in rural Taiwan I ended up taking a 4 hour detour to find the location in a larger city.
Mastercard has an online tool to find ATMs part of their network which helped me get started but it still takes many tries even when I found the ATM and it had the Mastercard logo, sometimes it just did not work for me.
Visa is only slightly less used but if you have both, then you can edge your luck. Even having two of the same type helps. It did not happen to me anywhere in Asia, but in Iceland, a HSBC Mastercard worked by not Citibank for transactions that required a PIN.
Yes, as far as I'm aware you can use a MasterCard to withdraw money at some ATMs in every Asian country except North Korea and Iran.
Beware that in some countries, notably Japan, South Korea and Myanmar, not all ATMs will accept foreign cards. In most, though, virtually every ATM will sport the familiar MC logo.