Yes, though slowly. Three to five years is typical for a sealed bottle and less once opened. Citrus and lighter scents turn first. If the color has darkened noticeably or the opening smells sharp and metallic, it has gone.

Somewhere dark, cool and dry, which rules out the bathroom and the windowsill. Heat and light break down aromatic compounds faster than anything else. The original box is not packaging, it is protection.

Skin, mostly. Your warmth is what develops the scent and fabric cannot do that. A little on clothing lasts longer but stays flat, and oils can mark silk and pale fabrics.

A smaller amount of a fragrance transferred into a plain travel atomizer. Useful for trying something before committing to a full bottle. Buy them from sellers who say plainly that is what they are.

Not the same thing. A clone is an original product, sold under its own brand name, formulated to smell similar to something famous. That is legal, because a scent itself is barely protectable. A fake is a copy sold under the other brand's name and packaging. The test is the name on the bottle.

Two to four for an eau de parfum. One or two for a parfum. If people tell you they can smell you arriving, it is too many, and you will be the last person to notice.