How do i upgrade my developer edition org to the latest Salesforce version? I have a developer org which is winter 14 and i would like to upgrade it to spring 14. Is there any option in administration to do this?
Upgrades between releases (API versions) is not something you can do yourself.
Salesforce does this for you and all other production orgs at the same pod at the same time. These moments may vary between servers (pods) and are always announced per mail to administrators and publicly readable on the trust website.