Sorry that my question apears to be unclear. I already have the synchronisation in place (API calls from Screenly or other software (screen synchronising)) but mainly does it work. I see the answer of Matrix, and I conclude it does not run on boot (answer to my 1st question) and I gather from you that there are no options to have 2 instances of screenly running at this time, nor are they currently planned.
Thanks you for your answers.