How to best manage multiple employees clocking in and out at once?

Example: A manager with the app and 10 employees with enrolled FIGs all show up to work at 8:00 AM, What is the most efficient method for all 10 to get clocked in?

The employees should begin checking in one after the other. The next employee should only swipe after the manager confirms the clock in of the previous employee.

Does every worker need to take turns swiping?

How far away can an employee be from the smartphone to have an effective clock in?
30 Feet at the most, the closer the stronger the signal communication

If the manager wants to leave his phone in a central location all day, acting like a kiosk, will employees be able to clock in and out throughout the day?
As long as the phone remains unlocked and the application remains open, yes.

If the managers phone does not have cell service, can employees can still clock in, and will there be geopositioning established?

If the phone loses cell connection, but maintains GPS connection, there will be no issue at all. If there is no GPS connection, the mobile device will attempt to connect via cell connection, and if that fails, it will check its location via wi-fi.