What, if anything, would have been different if the nurse had not been created? Would the ending be different? Why or why not?

I'm assuming you're referring to Romeo and Juliet. I t/would say the ending would be different because she was the one who allowed them to see each other they would have still been alive if they hadn't seen each other.

If the Nurse hadn't been in the play then Romeo and Juliet might not have died. She was the one who allowed them to see each other, if she hadn't they might not have been able to elope and then they might have simply fallen out of love. There's no way to know whether or not they would've found a way around the social problems.