1) Does the site counts only registered members or if somebody unregistered enters the thread he'll give +1 to the number of thread views?
It counts only if a registrated member enters your topic, not registrated members won't count. You can check it easily, if you log out and enter a topic, the counter doesn't change. If you are logged in the counter goes up.
2) And if the site counts every member for 1 or if a person would enter the thread for 5 times per minute the number of views will rapidly increase?
It doesen't work to click your post several times in a row - to avoid cheating. The counter will be stuck at the original number of views, even if you click 10 times. You have first to read another topic.
I just see so much average and boring projects in announcements but they have a fantastic views numbers and tons of pages with "oh, nice project, I will follow!" so that makes me doubt that project is not increasing its forum popularity with a help of some sort of ... cheating let's call it.
This is a big problem and maybe some projects pay for this "bumping" obviously. This creates a big amount of shitposts like "nice project", "very interesting project" or just "when moon?"