Frequently Asked Questions in Regard to Bluetooth Earbuds

The earbuds cannot turn on automatically when I dropped them out of charging cabin.
It seems that the right earbud ran out sooner than the left one.
The left and right earbuds could not pair automatically when I turned them on.
It is said that the earphones have noise reduction function but ambient noise isn't reduced when I put them on.
I have made connection with my smartphone for many times, but it failed.
During my runs, I found that the earbuds disconnected from cellphone for seconds at a time.
I only use one at a time, if I leave one in the box with it over charge the battery and drain the cell?
Can I use one earbud and charge the other when battery is low?
How far does the Bluetooth signal pick up?