Remove stains from seats and cigarette smell

Hello, yesterday I had some passengers in my Golf 6 with the bright seat covers: http://data.motor-talk.de/…/img-2227-58516.JPG Unfortunately there was a stain on the seat of about 5-7cm diameter. The edges are a bit black. Don’t know how and why it was created, let alone what should have gone out there. Either a little cola, rainwater from the clothes or clothes dyed by wetness. My Golf 4 with the dark seats has many white (also larger) spots on the seats through various liquids (NO, not THE liquid). How can you remove them best? Have found different methods: by means of steam cleaner, carpet cleaner, shaving foam… Second thing: My Golf 6 smells a bit of cigarette smell in the interior. No idea if the previous owner smoked, the building of the VW knuckle in any case smelled strongly after cigarettes. Could be that the smell has settled in the vehicle. What does it help against it?