Multi Location functionalities

One of the major requirements of my ecommerce project is multi country, multi region and multi cities.
So lets say am starting with 3 countries and the homepage is always defaulting to a particular country, how will people in the remaining countries that the homepage does not default o their countries know that the website covers their country as well?. Unless they click on the ‘Change Location’ they will never be aware that the website carters for them also.

So my request is to know whether there is a mechanism to make the homepage default to each country based on the geographical location of the visitor. like if a visitor is currently located in the country Ghana, then Ghana listings should default, likewise if the visitor is currently located in Nigeria, then Nigeria Listings should default and so forth.

however if the visitor is not located in any of the countries in the website then an agreed default country can display.

Finally is it possible to display all the multi countries in the homepage or header .

Regards

John.