No. A BMX is almost entirely ridden "out of the saddle" (=standing up), so size doesn't mean that much. (most) MTBs are intended for some seated riding, which makes frame size much more important.
Basically the same as road bikes, but with thicker tubes and bigger welds.
For better traction. Street bikes are made to ride on concrete and tarmac. Pretty much the same terrain everywhere. Mountain bikes are made to ride on dirt, mud, gravel, sticks, rocks, grass - and to get traction on those types of surfaces you need a wider, knobblier tire.
Not specifically. If you're a woman, don't let that bother you though, as most "women specific" bikes are the same as the mens bikes - only in smaller sizes and in "cuter" color schemes. Whatever your gender you can buy pretty much any bike of appropriately the right size, be ready to change the stem and the saddle and you're good to ride.
Both the Eastern Bluebird and Mountain Bluebirds are about 7". Approx. the same sizes.
BITD you certainly could. Since the pedals turned at the same speed as the wheel, people wanted as big wheels as possible. And since they were direct-drive, front Wheels couldn't have a bigger radius than the leg length of the rider. And since riders came in different sizes, the bikes came in different sizes.
Same reason Indy cars aren't built like off-road cars, they're meant to be used for different purposes. Road bikes are meant to travel fast on hard, smooth surfaces, while mountain bikes are meant to travel slower on uneven, loose ground. Different uses, different designs. What you need to do good under one set of circumstances might not be that useful under another set of circumstances.
you have to pay attention to the frame style and chain guard. a lot of retailers all had bikes made by the cleveland welding co. my 59 roadmaster ff has the same frame as a columbia from the same year only diff was chainguard and finishing parts and tags of course.
They have the same range of bikes as anywhere else. Road bikes, MTBs, BMXes etc etc
A woman's bike traditionally did not have the horizontal crossbar that was present on a man's bike. This was due to modesty and the fact that women wore dresses. Today however, many women are riding the same bikes as men. Another difference is that a woman's bike usually has a smaller frame size because women on average are not as tall as men.
Basically the same as road bikes, but with thicker tubes and bigger welds.
AFAIK, the 92 frame sizes have not changed
partly to help identify stolen bikes as you cannot change them but so criminals are not as dumb as people think and just file the code off and the same with the frame number