How can I tell which release my Salesforce Org is running?

 There are different ways can figure out ,The below one works always.

 1.Login Salesforce Org --> Set Up --> Company Information -->Instance 

2.Open " trust.salesforce.com" -->Scroll down to see status.salesforce.com --> Click on status button click --> search with company instance --> Shows the instance result --> click on the green check link --> Right side it show the Instance Details.