Yes, it recognises it partly automatically based on your movements. Otherwise, you can only enter it manually in the app. (Has no buttons for start/stop).

For product support, please contact the manufacturer fitbit or Huawei directly.

I'm not quite sure what you mean by fitbit Alta One.... Alta and One are two different products from Fitbit. There is no product called Alta One. Do you perhaps mean the "normal" fitbit Alta (S, Black) then the answer would be yes. PS: The fitbit One is only a clip and not a wristband tracker: fitbit One (Black)

Unfortunately, no. Fitbit has not yet built don't even interface.

The sensors are on the wristband. If the wristband is not worn, the band does not detect any movement.

i can only tell you the comparison between the charge hr and the alta hr - i find them more intense.

Doesn't have a GPS in it. If you take your mobile phone with you, you can use the phone's GPS for this, but you have to start and stop it manually, quite a hassle. Luckily I don't need the functionality :) https://help.fitbit.com/articles/en_US/Help_article/2099?l=en_US&fs=RelatedArticle