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