I have installed the plug-in but i dont see the same screen than the latest version.

Check what version is running in the Librairies in use dialog box shown when you click on the Libraries button in About dialog box. If it's not the good version, install the version 1.1 of the plug-in and don't forget to restart Sweet Home 3D.

Would you consider having negative elevation to make holes?

I don't think this will happen, but you can create a room at a lower level (including levels with a negative elevation), elevate all the points in the plug-in and finally dig a hole in this terrain.
See this video for more details.

I do not see the wireframe option, is it because i am using the French version?

The wireframe option is available only from version 1.1 of the plug-in and when there are some walls, rooms and furniture to display.