What you can do is putting the general part in a submicroflow. Then you have to model three different microflows which triggers the general submicroflow. Then you can end up the 3 specific microflows with opening the different desired forms.
Stil you have to make 3 different microflows in which you trigger the submicroflow. For maintenance purposes, you only have to maintain the general submicroflow. As far as I know, it's not possbile to conditionally navigate through a microflow depending on where that microflow was called from.