+1 for teaching Lisp to 5th graders. And have fun! Lisp, like Logo, is good for kids.
Your question is a bit rambling. (Emacs.SE is not a place for tutorials or discussions - it's really for specific Q & A.)
I recommend that you take a look at the manual An Introduction to Programming in Emacs Lisp, by using C-h i and choosing Emacs Lisp Intro. Work ...
The error seems to be saying that ((\, "http://melpa.org/packages/")) doesn't match the regex "\`https?:"
Let's look at that value, the one being added to package-archives:
If we put this into IELM, let's see what we get:
ELISP> '("melpa", "https://melpa.org/packages")
You need to format your numbers with the leading zeros if you want them:
(format "%03d" 3)
When you type
(defvar foo '(00 01 02))
and evaluate it, Emacs reads the string "01" and recognizes it as a
number (integer) and stores it in the list. Then it promptly forgets
how the number was represented - as "1" or "01" or "000001".
Included with emacs is a basic tool called picture-mode:
To edit a picture made out of text characters (for example, a picture of
the division of a register into fields, as a comment in a program), use
the command ‘M-x picture-mode’ to enter Picture mode.
In Picture mode, editing is based on the “quarter-plane” model of
text, according to which ...