Mohammed,
1. What do you mean not all the default basemaps are available?
The BasemapGallery widget displays a collection images representing basemaps from ArcGIS.com or a user-defined set of map or image services.
2. You can watch the basemap property or just check the basemap property.
map.watch('basemap', function(evt){
console.info(evt.title);
});
console.info(map.basemap.title);