No. Once the trial period ends, you will be on the Free Limited plan. You will not be charged.

This is normally due to the Google play store account used to download the app does not have the payment set up. You can go to google's site to confirm your account status.
https://myaccount.google.com/payments-and-subscriptions

Yes, choose "restore" purchase will allow transfer the plan between the devices when you need to. There is no limit on the number of allowed transfers.

The app is free in Limited plan, and is paid in Standard Plan.

Football (Soccer in the US), Basketball, Field Hockey, Lacrosse, Rugby

Yes, you can! The coach that created the team will automatically be a team admin and could upload the team to cloud storage and share with fellow coaches. Team information including lineups, custom formation ( player pictures not included right now) and game history are shared.

Android and iOS cannot reliably transfer app data reliably using the standard device data transfer process. You may share your existing teams to the cloud storage and then add easy team via the generated invitation codes.

Yes, you may add it during the game, or in the game summary events after the game finished.

If there are too much data on the device, it may lead to issues writing data to the device. You may recover the lost data by go to setting-> "View Data Auto Backup" to recover the most recently saved data. After that export and clean up unneeded games to prevent the issue from happening again.

Your feedback is always welcomed! Please send all you inquiries and suggestions to gametimesapp@gmail.com.

On iphone, ios forces the app to use the native "Mail" app regardless of which app is set as default mail app. Here is the instruction to set it up. https://support.apple.com/en-us/HT201320

You may upload from one device and download from another. Here is the tutorial https://youtu.be/rJE4vHZeNW0