Typically, an angler working upstream has the right of way over an angler working downstream and the downstream angler should yield within 50 yards or so and move to the downstream side of the upstream working angler.
Assuming that everyone is working upstream.
Question one: When you see people ahead of you fishing, you should leave the water to work upstream of them. It is acceptable to talk as you pass. How you doing? Doing any good? Wonderful day isn't it? Small talk is good and here in our neck of the woods most folks are friendly enough that they'll quit fishing to chat with you for a few. Continue to head upstream leaving the other anglers at least 100 yds of untouch water if possible.
Question two. No. Water is water and folks who are fishing the water will feel infringed apon whether it's along the road or ten miles from nowhere.
Question three. If the angler saw you fishing upstream and puts in just upstream of you without leaving you any fresh water.....well that's rude. You can be the better man and leap above them....while leaving them 100 yds of fresh water. Refrain from making rude comments as you go by....if anything mention to him that your going on upstream but will leave plenty of fresh water for them to fish.
Question four. If they beat you to the water you planned on fishing. Go with plan two. LEaving them plenty of fresh water if you head upstream of them, or just start well downstream of them.
Question 5. Yes and no. The guide is there trying to make a living. The client could be a green beginner or a seasoned vet. Special considerations should be given to them, however....if you follow the answers to the above questions you should be looked apon as a very gentlemenly angler. On a side note....the guide/clients should display great etiquette as people who fish with guides learn a lot about how to act while in the presence of a guide. Feel free to speak as you go by and wish each other well.
Question 6. I'll answer your question with one of my own. In the words of the great Roy D. Mercer......"Well how big a boy are you"?
No actually, no matter how rude someone else is.....there's never a situation that should end up with blows. Some folks just don't know any better, in which case maybe they'll learn by the example you set by always being a gentlemen displaying courteous behavior while on the stream.
Hope this helps.