For sure when you're starting out, it takes 10x as long because you have to google how to do everything! Very brave of you to use game jams as a way to learn gamedev, the pressure would have been way too much for me when I started.
I don't think you really need to worry about copyright in a game jam, I assume that rule is just to encourage creativity (and to prevent blatant theft).
But you evidently didn't need premade assets anyway, as you clearly have the skill to make your own art - it's actually kinda similar to my style, if a little more pixel-arty.