if you're currently doing another run, then yes, you have to reset.
Only genocide and Flowey the flower are violent because they are an important part of the story
If you leave any area without killing all monsters, or spare any of the boss characters, then you break the Genocide run. If you kill all monsters in the Hotlands, then you will face Mettaton EX who cannot be spared, and will die in a single hit. If you do not kill all monsters in the Hotlands, then you will face the normal Mettaton boss fight, and the Genocide run will be broken, you will go on a Neutral path. Because you're then on a neutral run, you do not get the Sans boss fight. His ending comments will mention all the deaths you caused.
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.
reset run flat indicator
A lot
omega flowey
yes
Yes but no at the same time
Sans
Juvenal Habyarimna was the president his plane waas shot down by attackers and then the genocide started run by RPF.
Sun Flower
yes yes he did