is there support for geo fencing on Android if yes then what is the earliest platform that support Geo fencing feature.
By Google Maps, do you mean the Android location manager? The Google Maps application itself doesn't appear to have that feature built in.
Depending on what you're planning to use it for, you could most definitely implement a simple geofencing feature yourself using the GPS libraries (i.e. LocationManager) and a simple collision detection algorithm like point-in-polygon or a bounding box check, and display it on a map control.