I have forgotten the name and tags, so no help there.

Discord turns a human into a changeling, and sends him back to just after his first defeat.
He helps Luna not become Nightmare Moon, while also helping others in this post discorded world.

Time to list some crazy A-Z symptoms
First come, first serve

A
Burping Bubbles (had a bar for breakfast)ANW
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z

Light and dark reunited.
Yet she was the one to raise me from my shadow.
Who am I, and what was my shadow?