The error means that the http response 405 Method not allowed was received.
Do you connect directly to the Internet or through a proxy server or firewall? Could you try connecting trough a different ISP?
No. The license will be valid for 1 or 2 years, depending on what license you purchase and will enable you to install ESET on 3 devices. We do not sell licenses for 3 years and 2 years are maximum to my best knowledge.