tombeii

In the apearence menu, go to fifteens settings, the page has tabs. Choose the social tab and add your credentials

ad 1: You have to go to each post for which you want picture on the home screen, at the bottom of the edit post page to the right you, can add a thumbnail picture from your media libary, this will show as picture on the home screen.

ad 2: I dont know ??

ad 3: the menues are site based, so when you create a new site it will show as menue link

If you create a new empty menue and asigne it to the part you want to get rid of, it will no longer show.