Generally speaking aluminum frames have larger diameter tubes than steel or titanium bikes, but the most obvious is to test with a magnet. If it sticks it's a steel frame. If it doesn't it's probably aluminum. Titanium frames are still so rare that you are very unlikely to buy one w/o knowing.
A street bike is a type of BMX bike, so your question can't be answered.
The type of bike that is mostly used form BMX riding are the purpose-built BMX bikes.
A Harro is type of BMX bike
BMX bikes pretty much all have 20"wheels, which makes all frames very similar in size. On top of that BMX is almost entirely ridden standing up, so bike size doesn't matter as much as it does for road riding for instance.
to be honest gt biek frames suck, their company is just poor and they need money for their thirty pound frames. that is why they are about 300 dollars and 800 for a complete bike get a premium if you are looking for a good bmx company
you can find a BMX bike in halfords
well it all depends on what type of BMX you do. For me i do park and vert. And i use a fit bike. But for flat land the best type would me strowler. But like i said these so many diff rent forms of BMX.
The bmx thruster rampage bike is a exellent bike
One can buy a custom BMX bike in Las Vegas from a few stores. One can get a BMX custom made from 'Just BMX', 'Bolder BMX', 'Bike World' and 'Vegas Bike Store'.
A hyper is better
no but you can get a dirt bike or a cruiser bike or a speed bike but i havnt seen a bmx bike yet.
A BMX bike is good for both boys and girls, as long as they want to do BMX-style riding, with jumps, tricks and that. If you don't want that, there are several bike types that are better, more comfortable, and more efficient for general riding-around type of use.