Cloning the repo vs building the docker container

[IdanBanani]

I couldn't find here nor on the website an explanation regarding the different options to work on the lab exercises ( /tools/labs).

There is no mention on whether one can use its existing environment (Ubuntu 20 virtual machine) and just copy to it the /tools/labs folder content

Correct me if I'm wrong:
A. You can/must/skip git clone this repo and build this specific old (custom?) kernel by yourself?
B. In case I wish to use the docker container (since I'm not there are instructions for the other way),
what sub folder is the minimum I need to download? /tools or /tools/labs/ ? ( I looked at the tools/labs/docker/docker-compose.yml volume mounting)

C.There are 2 dockerfiles (what is the point?) for ubuntu 20.04
tools/labs/docker/kernel/Dockerfile - No need to compile the kernel + no need to clone this repo?
tools/labs/docker/docs/Dockerfile