As several people have said pores do not open and close. Warm and hot water will loosen up dirt that is in them though and clean them better which is probably the feeling everyone mentions when they say something about opening pores. I learned this a while back when I was in the B&B chat, someone was kind enough to link me to a reputable article on the subject which I have unfortunately lost since . That YouTube video basically sums up the article I read.
As for the cold water, my face doesn't get dry until it air dries with my AS on it. So having hot water with the shower, then a splash of hot water before I lather, then a wet, hot towel, then hot water rinses between passes, finally some cold water on my face is FANTASTIC. The best was using QCS Vostok the other day, after my final pass I splashed some cold water on my face and the menthol instantly froze my face heh. It was quite refreshing and I think that is why I continue to do the cold water as my final rinse.
As for the cold water, my face doesn't get dry until it air dries with my AS on it. So having hot water with the shower, then a splash of hot water before I lather, then a wet, hot towel, then hot water rinses between passes, finally some cold water on my face is FANTASTIC. The best was using QCS Vostok the other day, after my final pass I splashed some cold water on my face and the menthol instantly froze my face heh. It was quite refreshing and I think that is why I continue to do the cold water as my final rinse.