how is it possible to place and activate/desactivate a module in its corresponding position ?

There are several ways to display desktop modules in positions of mobile template:
1. To duplicate the module in one of mobile template positions (mj_top, mj_top2, mj_top3, mj_middle, mj_middle2, mj_footer, mj_footer2, mj_panel).
2. To "proxy" it using the 'Mobile - Proxy Module" module (publish this module in a mobile position and set it to display specified module).
3. To "proxy" entire desktop position using the "Mobile - Proxy Position" (publish this module in a mobile position and set it to display modules from the specified desktop position).