Its not based on real events
Why wouldn't they is the real question.
No, unfortunately. He would be creepy if he was real so...thank god he is not.
Undertale was created by Toby Fox, a game developer for the Mother series. You can actually find him in Earthbound as a dog in the shop in Onett. After Undertale, he later went on to create Deltarune Chapter One. Toby Fox's true identity is yet to be fully revealed.
A lot
Yes but no at the same time
yes
Sans
yes yes he did
[object Object]
Undertale
Sun Flower
Toby Fox. He also I believe he "developed" Pokemon sun and moon, or sword and shield.