Welcome
I agree it will be helpful to buy a getting started booklet. Dave Whitlock also wrote one targeted for beginners " The LL Bean Fly fishing handbook". You can augment from the web but it is good to have one general overall source or it is hard to see the over all picture.
Tippet and leader. Fly fishing leaders are generally heavier near where it attaches to the fly line and thins toward the connection to the fly. These are called tapered leaders. You will have to learn a few knots if you want to make you own. Tippets are the lighter in lb test than the leader. If the light end of the leader is 5 lbs the tippet might be 3- 4lbs say for trout.
If a fly outfit is labeled 5/6 It means the rod is designed to cast a 5 weight double tapered(DT) line or a 6 weight weight forward (WF) line. Yes fly lines come in different shapes.
How you fish with flies depends on the conditions and the what the fly is supoose to imitate.there are volumes of books and debateson this subject. You can take a common cents approach.If you are fishing a streamer like a white wooly bugger which could suggest a minnow and minnows which swims so it is appropriate to strip in or move this type of fly. A small fly like a size 18 or smaller is generally more helpless in the water so especially in a stream with current it would just drift along with the current.
on small fish we generally do not use the reel and strip the fish so we can get our fly back in the water quicker. there is no rule that says you can't reel them in, but if you do you first have to reel up all you slack line, reel the fish in , and then strip line back out so you can cast again.
I did,nt really understand you last question.
If you have any ponds near you that have access to I would suggest started out fishing for bluegills in still water especially in the spring when they are aggressive. Current adds another demension to controling your line.learn how to cast either through a friend who is a good fly caster, or through lessons, or a video such as Dynamics of fly casting by Joan Wulff. Practice casting when you are on land and fish when you are on the water