Types of boundary conditions

[mobina99abc]

Hello

I am a beginner in machine learning and I did not find the answers of these questions by searching. Thank you for your guidance:

1- What is the difference between hard and soft boundary conditions in DeepXDE?
2- Does the periodic boundary condition mean a time-dependent boundary? It means that we have to use the periodic boundary when we have an external loading such as an earthquake wave?
3- When we make the grid points in a 2D DeepXDE, how to graphically see the distribution of the grid points in the domain and on the boundaries?

Thank you