Why don’t I have any friends

It still means the number of floors you each have. It doesn't automatically sync every time you look at that page - I have had it be behind as much as 5 floors early on when I was building a lot. I suspect it only syncs a certain number of times per day.

As for your friend - there may be a problem with him syncing - perhaps he isn't connecting to Game Center, or has been offline when it is syncing, so you wouldn't see his floors. I know that sometimes it takes a couple of days for that screen to match what I see when I view my friend's towers, or for it to match how many floors their game says they have.

The great things about bitizens is that they never seem to need to sleep. Thankfully you don't have to manage your bitizens personal concerns in this game, as the focus is the tower. Your bitizens will work 24/7 without any loss of productivity, so long as you can keep your shops stocked. So, yes, shops should be open at all times.

If you see them complaining in the Bitbook, I think that's just the developers way of adding some personality into the game. :) The only way to make a bitizen happy in the game is to employ them in their dream job. Failing that, until their dream job opens in your tower, best practice is to match them with the area that they are highest in according to their profile. They will at least remain content until such time as their dream job opens and you reassign them. So long as you can match them with a job of interest level 5 or greater, they will be content. Anything less than 5 and they will be unhappy in their job.