Codes that you’ve experimented with don’t count.
You can learn as much as you want before the Jam and experiment as much as you want before the Jam. But any actual super custom coding for the story should be done during the Jam.
For example, in Ren’Py, you can learn how to use LayeredImages to assemble and display sprites. You can use placeholder images to learn, such as previous MAY WOLF premade assets, but you shouldn’t then copy-and-paste all of the code that you were using to learn, for the Jam.
Another example would be if you want to make a VN/RPG Hybrid, you can experiment with making a RPG Battle and Inventory System as long as anything very specifically related to the story and Jam entry isn’t done until the Jam starts.
Will answer the other part soon.