OneSignal - What do users sign up for?

While setting up the OneSignal I am made aware that the end user has to accept the subscription, which leads to these question:

1) when a user subscribes is there only one feed from Easyblog they sign up for?
2) if there is more than one feed do they have to sign up for more?
3) Are Easblog inbuilt comments classed as a seperate feed?
4) With the questions above in mind is it still correct to have Komento use the same App from OneSignal?
5) Does easy blog support all mobile devices? Do I just need to finish setting them up in OneSignal?
6) Do you have instructions onhow to integrate OneSignal with Google Analytics?
7) in your onesignal instructions there is the following statement "Unzip the OneSignal-Web-SDK-HTTPS-Integration-Files.zip file and you will find these 3 files: , manifest.json (You will need to edit this file)" Do do not say what to edit and what to replace them with. Can you tell me what I should change?
8) where do i get my gcm_sender_id from?

NB: Onesignal have changes their setup procedure so you guys might want to have a look at that.

Thanks