2.How do you know what theme a person is using on their website?
You can use a site like http://whatwpthemeisthat.com/. and if its not a wordpress one it will identify which provider probably designed it.
3.How do you know who owns a website or if it's likely to be a legitimate one? or if the person is a longtime in business or two weeks or so? Then check out. https://who.is/