Yes, by all means make a group booking. But each person must have their own ticket and their own cellphone.
You will start one by one, shortly after one another, and your start locations will be different. However, you will all be headed into the same part of the city, and are likely to finish very near each other.
Yes. If you would like to use your own phone, you are welcome to do so, but will be charged roaming rates for about 40 minutes of calls.
We do have a number of loan phones available free of charge – however there is no reservation system for these, and so you may incur a wait for these become available. Maximum wait time for these could be 75 minutes.