No bikes allowed inside is often a lease term that is completely unenforceable. So if it's a landlord telling you that, just ignore it. Especially if you're cleaning the bike before you take it inside. You'd be responsible for any damage to his property but that's true if you take a playstation inside.

If he said "No playstations you have to buy an xbox" you wouldn't, would you?

Pro teams used compressed air to blow the water off and out of bolt heads etc. You can use things like bike shine and other water displacement products. Obviously relube the drive chain.

Depends on what the bikes parts are made of. Obviously carbon and alu frames won't typically rust, you can titanium bolts (although I tend to find the only bolts that rust are the ones that you've used a few times, i.e the seat bolt - possibly because the others have some kind of coating that the tool removes after a few uses)

The drive chain is protected with lube. The issue with keeping a bike outside is really from it being exposed to the weather, snow, rain etc rather than because you wash it. If temperatures drop freezing water will expand possibly damaging parts.