Go to Pyramid Air, you can browse and read about all of them. I bought my Diana RWS with a Hawke scope. They have package deals where they will mount the scope and sight it in. read up, there is allot to learn about a higher grade pellet rifle. Especially the proper scope mounts
Or, you can go to Academy and get a middle of the road gun, the Beeman Teton piston rifle.
you could leave on cocked but really no need too.
depends on the size of your targets and if you want to kill it. I used to have a feral cat problem when I was a kid. I had a Sheridan Blue Streak. I would pump it 3 times and shoot these cats in the butt, they would screech but pellet would not penetrate. Same rifle claimed a ton of robins, sparrows and cedar wax wings every afternoon when I was a kid, a bad kid
"I ain't here for a long time, I'm here for a good time"
King George Strait