can anyone tell which are the countries still dont have a mobile phone service when you visit that country?

Answer 1

Most "underdeveloped" countries have jumped from no phones to cellular in the past decade bypassing land lines in remote areas. In fact a lot of these countries have cell service that is 2 generations ahead of what we currently use.
What you should be asking is whether your North American phone will work anywhere else in the world. Keeping in mind that even between Canada and the US your phone won't work when you cross the border unless there is an agreement between providers