If the ram is the exact same kind and size then it will work in dual channel if otherwise it will then just work in single channel.
Also make sure that the matching stick are placed in the same two slots for dual channel to work.
Not to be rude, but you should look up "dual channel RAM" sometime. You can't have a dual-channel RAM setup with only one stick of RAM.
As for the rest of your question, to be honest, you'll seriously have to get out your mobo manual and read the section on the RAM slot specs. Not all boards support DC, and some boards only support DC for 2 sticks, not 4.