I have permissions for everything but they don't care, as long as I don't make it, it's reused. I have this channel since 2008, it's actually a great channel, I don't do it only for the money, I made a DJ carrier thanks to it.
For your second question, well if you put a video which gets lots of views read - viral video) on private and than put it back on public after some time, it won't get that many views anymore, probably because it won't be suggested anymore. That's why I chose unpopular videos, because they're irrelevant for my channel.
Edit - yes, it's a music promotion channel