This is my first time writing out a pattern, it has been tested and mistakes amended.

The needle size is not a big issue for this project as it is very versatile.
If you have a yarn you really want to use and it requires a size 4mm hook, then you can use it, same for size 6mm yarn, use a size 6mm hook.
The smaller the hook the smaller the end result. The larger the hook the larger the end result.