1. Does your miner work without reward to the developer?

I am not going to answer this one.

2. How can I find out about hardware errors? (For example, as in the Gateless Gate field HW)
3. How can I find out about the complexity of the shares?
To be implemented.
I will look into this.
6. How to connect to European pools without using the Custom tabs
GGS automatically chooses the server with the fastest response time.
In your case, a server outside Europe responded more quickly than European servers.