Activating the genocide route [closed]

So I just finished true pacifist route, and I planned on doing the genocide route now. I understood that I must keep killing monsters until the "But nobody came" text comes and music changes, so i kept killing. I also slaughtered the dummy and the froggit that appeared during Toriel's "walkthrough", but it doesn't matter how many monsters I kill, the route wont activate. I have some questions about it.

1.Am I allowed to "kill" Napstablook if the genocide route is not activated yet?

2.Am I allowed to leave the first room (you know, with the monster candy room and a leaf pile in it)I left it and saved my file at the mouse hole part, but if I'm not allowed to exit the first room I guess I screwed up.

3.Can I complete the genocide route after a true reset? Or do I have to complete the neutral route first?

[Obvious Genocide route spoilers below]

To get on the Genocide route, you have to actively hunt for as many monsters as you can find. That means you have to kill not just the scripted monster encounters (such as the Froggit or Napstablook) but also a certain number of random monster encounters. Additionally, you have to make sure you kill enough monsters before you fight the boss of the area. For the Ruins, this is Toriel. Papyrus is the boss of Snowdin, Undyne for Waterfall, and Metatton NEO for Hotlands. If you don't kill enough monsters before killing the boss, you will get shifted to the Neutral route.

After you kill enough monsters in the Ruins (you'll know you've killed enough when you get the "But nobody came" message), all future save points will show you how many monsters you still need to kill for the current region you are in. Once you've killed enough monsters, the save points will simply say "Determination.".

As long as you follow these rules, you should stay on Genocide route.