exist

Is there only one domain name exist? I mean I searched on different registrar and I find different prices on a certain domain name I plan to buy. Does that mean that if I buy domain, for example, on namecheap. Would it still be available on godaddy? Please help.

hello, i want to add a script that show some alert for visitors when they try to close the page, can google penalise my website for this script? thanks.