Three.js Walk the route

I looked at the topics on the forum related to this issue. I found something approximate.
Interested in 2 questions.

  1. How to make such a movement of the camera by clicking on the floor?
    In this example, movement along parts of the floor, but you need to calculate the coordinates of the floor and only then direct the camera there.

2)Сircle is attached to the cursor, which only appears when hovering over the floor.
how can this be done?
found this option. Can he come up?