3-9 LIEs
ELF-MONSTER-BEAUTY
FEEL-CALLOUS
FILE-CUSP
FILL-SUBSIDE-BOIL-FREEZE

TAKE-GIVE
SAD-CHEERFUL
MINOR-MAJOR
REAL-FAKE
NOISY-QUIET
UP-DOWN
SIMPLE-COMPLEX

The place we need to get to is the stage 9 in chapter 3 (4 more stages to the final boss fight).

Obviously, we can use the letters E, L, I and F freely (almost) here.

If you've been here by yourself, you must have known that the word LIE would become a tiny robot, and can transform one of some words into its opposite (maybe...sometimes not so logically) word by react with them.
Now we have L, I, E, and an F. Time to craft an alphabet!

First of all, we have E, F, L and I, which could be call "Lv.0 letters" because we can use it directly.
Next, we can use these LIE-react-chains:
ELF-MONSTER-BEAUTY
FEEL-CALLOUS
FILE-CUSP
FILL-SUBSIDE-BOIL-FREEZE
to get the letters A, B, C, D, M, N, O, P, R, S, T, U, Y and Z, which could be call "Lv.1 letters" because we don't have to take out any letter in the words that we just crafted before getting them.
Now we're able to craft any word without letter G, H, J, K, Q, V, W or X in it.
Then here comes the hardest part.
We can use these LIE-react-chains:
TAKE-GIVE
SAD-CHEERFUL(I thought it would be HAPPY lol)
MINOR-MAJOR
REAL-FAKE
NOISY-QUIET
UP-DOWN
SIMPLE-COMPLEX
to get the rest of the letters. BTW, H, J, K, Q, W and X are "Lv.2 letters", G and V are "Lv.3 letters" in these react web.

(I was trying to craft a alphabet without using the rebirthable letter on the right side but fail because of the lag.)

Have fun or have a rest.
Thanks for reading ;)