A:AnswerI had the same problem when I traded in my old Apple Watch. I just chose a close model and when I brought my watch in they had no trouble giving me the full amount allowed.
A:AnswerAccording to Apple, it does not. Whoever wrote "LOL" needs to get a life. The O2 sensor is important to many, although it may not be as reliable as the kind you put on your finger.
A:AnswerGo to Apple and download the band sizing page. It is fairly easy to figure out your band size then.
https://www.apple.com/shop/Catalog/US/Images/bxxd/size-guide_CA.pdf