Connection level of K2 in SharePoint is configured in Site collection level.
If you want to connect K2 Dev and K2 test environment to Same SharPoint site, it will possible.
You can create 1 site collection for K2 Dev and configure that SC to k2 Dev
Similarly You can create 1 site collection for K2 Test and configure that SC to k2 Test
samw way for UAT
K2 process template is new template which is related to k2