Can we develop android games with GDevelop and monetize them with ads etc?
GD can export games to HTML5, then you can export to Android through Intel XDK:
Intel XDK on the wiki
About the ads, GD desn’t support them, but maybe you can use ads through Intel XDK 
Does exists some games available for test ? I’m curious about the layouts on different mobile device.
Unfortunately, not.
In any case, I’d not use GD for Android gamedev yet because it still doesn’t have any Android-specific features such as access to gyroscope/accelerometer, multitouch (single touch is there, mouse click events are translated to touch) and ads/iaps.
What are the supported event ?
Tap ?
Double tap ?
Swype ? (Giving a move with finger ?)
Long push (pressed ?)
Drag and drop ?
About the ads i think it’s possible directly from the html 5 render then manually add it and convert the project into apps with some external tools, or by integrating it with phonegap or android sdk.
You can code it yourself. Tap=mouse click event, double tap=clicking fast in short amount of time, swipes are all about comparing coordinates of where mouse was pressed and where it was released, long push is about calculating time mouse button was pressed and as for drag and drop, there’s automatism for that.
Things that you CAN’T code now:
- Multitouch
- Ads
- IAPs
- Accelerometer/gyroscope support.
I’d be more worried about above list.