Q1: It won't work with DTS DVDs.

Q2: You just need to connect either of the first two if you want your receiver to do the decoding or the last one if you want the DVD player to do the decoding.

Q3: You can make your own S-Link cables, or you can go down to your local Radio Shack and pick up some cable with a mono 1/8" mini jack on either end.

Q4: Not sure on this one, but apparently the A1 control is an "enhanced" S-Link.