Go to your google account, and check the security section to see if there are any applications that you have granted access to.
It is a good thing to check this every so often to make sure you haven't accidentally granted access to something you didn't intend to.
I don't Think so. What you can do is mark your video as unlisted and then share the link with the people you want to see the video. However, What you want can be done in vimeo, check there website for details.