2. I've personally never done it, but to each their own. I don't think it would be a good idea though. Traditional application points include the sides of the neck, back of the neck, chest, and wrists.
3. It varies really among fragrances. It really depends on the type of fragrance and ingredients used. Generally a fragrance that has gone bad with smell similar to a fresh bottle, but weaker.
4. It doesn't hurt shelf life that's for sure. Primes enemies of fragrances tend to be heat and sunlight. A fridge eliminates this, but you could just keep them in a enclosed cabinet or something if you don't want to put them in a fridge.
5. I think it means that information has been submitted for that particular fragrance. You can find the information under the "Basenotes Says" heading.
6. Usually it is not advisable to mix fragrances in their bottles. People do mix fragrances when applying them though. It's called layering and someone more acquainted with it will have to go into more detail about it.