What version of DD4T does DXA 1.2 use? And where can I find this information?
I am assuming that you are requesting for the DD4T version in the CMS side (TridionTemplating). Based on the updated DD4T DDL for DXA 1.2 "DD4T.Templates.merged.dll" in the CME, it is using 18.104.22.168. The source code is available at https://github.com/dd4t/DD4T.TridionTemplates/tree/2.0.4-beta1.
The Content delivery DD4T core solution is available at https://github.com/dd4t/DD4T.Core.