Wall thickness is about one mm.
No
The most common metal used for standard bicycle frames is steel, although it is possible to get frames made from graphite, aluminum, and titanium alloy.
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.
Motobecane frames are made by Kinesis in Taiwan. Kinesis also makes the bicycle frames for Jamis, Specialized, Schwinn, Felt, and other well known bicycle brands.
Magnesium, Titanium
Oh sure. Carbon fiber frames are composites, and quite popular.
Chromoly (often spelled cromoly) is an abbreviation for "chromium-molybdenum steel". Chromoly is an alloy used to produce tubing for bicycle frames and race-car roll cages. It is not as lightweight as some steel alloys, but has the advantages of high tensile strength and malleability. It is also easily welded and is considerably stronger and more durable than standard (1020) steel tubing. It is also known as 4130 steel, and is composed of 0.28 to 0.33% carbon, 0.4 to 0.6% manganese, 0.8 to 1.1% chromium, 0.15 to 0.25% molybdenum, 0.04% phosphorus, 0.04% sulfur, and 0.2 to 0.35% silicon, in addition to iron. Retrieved from the link on the right
These days - usually not.
Both 6000- and 7000-series alloys can be used for bike frames.
There is no bicycle that is made out of Nickel. Some steel frames may be coated with Nickel only for aesthetic purposes.
Looking to purchase a bicycle frame without the accessories? Not all bicycle frames are made the same, therefore a low-quality bicycle frame can be purchased used for as low as 99 cents on ebay, while better quality frames may cost a few hundred dollars.
It is light and strong