A:AnswerNo, the i5-8400 is an 8th Gen Intel processor. This motherboard only works with 10th (i.e. ix-10xxx) or 11th (i.e. ix-11xxx) processors. You need something from the 300 series of motherboards like a Z370 or Z390 which you may have to find used since they were both discontinued a few years ago.
A:AnswerYes it will. This motherboard has an M.2 drive slot that will only work with the 11th gen i9 CPU. The motherboard will work with a 10th gen as well, but the M.2 slot will remain inactive without the 11th gen.