it means there is a problem with your xbox there is an error inside of it for instance the motherboard or it could be the hard drive
You can't, at least not yet anyway.
One can purchase an Xbox 360 Motherboard replacement from: iFixit, eBay, Aliexpress, Each Mall, Alibaba, Richs PSX Parts, Stack Exchange, to name a few. Prices start form $19.
DVD key? I think if you look on the DVD drive itself it may say something about a key.
New casing, a new chipset which helps it run cooler and redesigned motherboard and a revised DVD drive
Every Motherboard on the xbox 360 supports a code on the back of it representing the chipset. The Launch xbox 360 codenamed xenos says 16.5A 6 volts on the back. The Zephyr Motherboard says 16.5A 5 volts also but they just added HDMI. The Falcon says 14.2A 5 volts. The jasper the newest of all 12.1A 5 volts. You will need to do a little bit of searching around on the back of your xbox for the chipset code.
Yes, the motherboard (mainboard) of the Xbox 360 is defined as an advanced circuit board. Controllers, remotes and memory cards also have embedded circuit boards.
It's a long and complicated process. Mod in itself means "modify" so basically, you modify the motherboard and the internal workings of your xbox. I would hit up YouTube for a visual representation.
The cord could be broken or something on the motherboard could be broken. You could also check if all the cables are plugged in correctly into your TV.
An Xbox 360 or other gaming console (too) close to the modem will cause the modem (online) status connection to burn out.
No. As far as I know the chip is fixed onto the motherboard and as such if you want a Falcon you will have to buy an Xbox 360 that comes with one. Moreover, there's also the fact that you can't buy a Falcon chip on its own.
a motherboard