Can you check in at terminal d when you are flying out from terminal a? I ask because I want to stop at duty free before I fly back to canada.

Yes you can. Take skylink once through security. Skylink will take you to all of the other terminals.

Depends on the airlines u are using But i am sure If it is American . Then Yes

They are separate buildings best got to via car or bus. They are a ways apart and hard to get to or even dangerous to get to on foot depending on who you are and which ones you are going to. There are 2 on each side of street.

Ask at terminal

Better check in at A, and take the Skylink to D

I dont think you can