It depends on your operating system.
No, the iMac will not play a Blueray disc.
If you get the Mac Version, yes it will work.
No. You can only play games made for Mac OS on an iMac.
There is no Mac version of Maple Story but if you have a recent iMac with an Intel processor than you can run Windows on your iMac and play the Windows version of Maple Story - see related link below for details.
OBIVOUSLY THE iMAC
Im thinking of buying a imac g5 but I don't know if I can run Minecraft on it
It is not possible to convert a DVD into an iMac.
Yes
No it will not play a 6" disc. It will play a CD or DVD.
Only if you have a Mac version of this game or you have the Windows version and you have Windows installed on your Intel iMac.
about 2 pounds