Is it right to evolve a friendship with the opposite sex into a "close" one when married? To the point of chatting with him/her first thing when you wake you up in the morning and the last thing you do at night when you don't even do it with your spouse? I call that cheating. What do you think?

Don’t agree with this. It’s emotionally cheating in my view, even though you think you might not have feelings. You will anticipate the person’s messages and the fact that you do it first thing when you wake up and last thing before sleep is not normal at all between even very “close” friends.. imo