Some, but not necessarily all. Bottom brackets and headsets for instance are available in several versions.
It's not really clear what you are asking about. But you can use the same components even if the material of the frame is different. Basically you can use the same parts in a steel frame as you would in an aluminum frame - assuming the physical fit is the same.
Any tyre that will fit the rim and clear the frame.
Almost 100% definitely not.
This is possible with some minor modifications to the bike's frame.
Yes you can but, depending on your frame, you'd need a shim to get the post to fit your frame.
if your gonna get a fit, dont get a 2010 model, they are designed to make you buy more and more fit products and most other parts never fit. if you can get a fit flow, there amazing dude.
MAYBE - , frame size has nothing to do with tire size. Style does, and if its a mountain bike, it will not work with a 27 (road racing) wheel and tire. Brakes will not fit.
i would go with a fit for a good frame any day but it really depends on what you really want for style or just brand name sometimes. Fly makes really good frames also and their cranks are he best in my opinion. To answer your question it really depends on which frames you would want to compare. Also comparing the warranty situations and which frame is lighter or stronger there are too many things you would have to consider not to mention the price your willing to pay for a frame, you question in unanswerable.
Size wise, it would fit, however it wont bolt into the frame if that is what you are asking.
they might its hard to say because there both the same size bike
Yes it is possible but if there is enough space. It will enhance the performance of the bike and it also increase the pick and speed of the machine.
Bicycle sizing is very personal, and depends on many different dimensions of your body, not just your height. A reputable bike shop will be able to offer you a fitting service. This can ensure that you get the right size of bike, including changing certain parts of the bike if necessary.