I wanted to know if it's possible to simulate the hibernate process of Ubuntu to save the entire state session into a file. Then to select which one to restore ?
In short, you can't.
When a system hibernates, it saves the contents of RAM into a swap file (as in Windows) or to a swap partition (as in Linux). Ubuntu could hibernate to a swap file.
However, you simply cannot have two hibernated states at the same time. When you hibernate, the RAM references little system writes that are going on as well as hard drive contents, etc. If you resume that state with those things changed, you'll screw up your system. Operating systems delete the hibernation data after resuming to prevent this.