Questions for Zero Plan and Helium network

Currently use a Helium Zero plan.

Questions:

1. 3GB free data per month, and the last 2GB should go through Helium network. How to go through Helium network?

2. I see a lot of "Helium" public wifi in the public location (e.g., plaza). Is it the Helium network?

3. If yes to Question 2, can I first take use of Helium network instead of regular 5G data network?

4. If yes to Question 2, can my another phone take use of Helium network/public wifi?