YOLOv5, YOLOv8 questions

I am working with yolov5 and i have some questions:

  1. How to process 4000 x 4000 image with yolov5? I guess yolov5 firstly resizes 4000x4000 image to 608x608 and then calculate output. Results with different resolutions are different.
  2. How to train yolov5 on custom dataset? Where to find dataset for yolov5?
  3. What is the output layer format of yolov5? Is it [width, height, class, competition] or like?