For testing, try putting your code in:
@supports (display: grid) { }
Then to make it all fail, change a letter, like:
@supports (display: xgrid) { }
Series on IE 11 fallbacks
https://rachelandrew.co.uk/css/cheatsheets/grid-fallbacks
http://codepen.io/chriscoyier/pen/MpEjba/
gridtoflex.com