Start new Solidworks session ever

How should be written the code (C#) for starting a new SW session even there are another living sessions?

This requires a stand-alone application, you cannot be an add-in since those run inside solidworks.

Then you need to start a new solidworks process, possibly wait a few seconds, then get the running solidworks application. For the last step, you need something like this:
var solidWorks = new (SldWorks) Marshal.GetActiveObject("SldWorks.Application");