Analysing Glimmerdemption: What Went Wrong?

'How do I start?'
'Starting is easy. CARE ABOUT SOMEPONY OTHER THAN YOURSELF! '

This, my friends, is another MLP analasys, this time of Starlight Glimmer, or more specifically,  Glimmerdemption, and why it all went horribly wrong.

Now, the first question is...Where do I begin?
I think I'll start with a basic outline of the scene just to jog our memories and give us some context. Excuse me for a second...

Now, in the minutes leading up to the redemption, Starlight offers us no reason to feel sympathy for her. She makes light of the idea that Equestria might be destroyed because of her actions, and doesn't give a damn about what Twilight is telling her. This was after the SIXTH alternate future Starlight created. When Twilight drags Starlight in the future, and they see the Equestria is now an apocalyptic wasteland. Twilight tells Starlight about how her friends have saved Equestria, and that without them countless futures could come to pass, good or bad.
For a few seconds, Starlight seems sad...until she goes right back to screaming her freaking head off about how Twilight doesn't know anything about her, how she was happy before the Mane 6 ruined what she built. From her screaming, and after everything we've seen, you'd expect a pretty harrowing backstory/excuse to justify her actions, wouldn't you?

That is not what we're shown. In fact, what we're shown isn't nearly emough to give Starlight deniability for her actions to any extent.

Leaving this for now, here are the four main reasons (and one extra) why Glimmerdemption didn't work. I'll ho through them in order from least to most important. Get ready, people, this is gonna be a long one. In fact, I think I'm leaving this as an introduction, and I'll make a part for every point.

1.  The rushed 1 minute 47 second solution.
2. The botched character development
3. The backstory and 'justification'
4. Starlight absolute selfishness

And the extra: The absolute horror this episode brings about due to fridge horror.

So, here's the introduction. In part 1, we'll discuss how rushed the redemption was, and why.