No, the builds are different. Only OEM & retail channel keys can be used across different builds (TH1, TH2, RS1, RS2.....). @jebbec https://forums.mydigitallife.net/threads/62707/
If you only have a 2015 key and want to install 2016, you can safely upgrade from 2015 to 2016 without any issue
I write all my keys on slips of paper. I put them in a hat, stand at the top of the stairs and dump them all out. The one that goes farthest is the x86 key!