[Vermin (Tom)]

1) Yes, even in light polluted cities. You can see Mercury, Venus, Mars, Jupiter and Saturn with the naked eye at certain times of year. You even can see some nearby galaxies with the naked eye (from a dark site), Andromeda, the Large Magelenic Cloud and the Small Magelenic Cloud for example.

2) Only one, named Sol (The Sun) the next nearest is about 4 light years away (Proxima Century).

3) Well spotted! It's the "Coal Sack", a big mass of inter stellar dust obscuring the background stars of our galaxy the Milky Way. There's actually quite a bit of this visible along the Milky Way's plane, from a really dark site with excellent transparency (no haze) and well dark adapted eyes this can look like a huge split in the sky!