Is there a reason you are buying 2400 MHz DDR4 when you're CPU only supports 2133 MHz?
Probably missed this one. Didn't know CPU's had issues with Ram compatibility. Both Pentium and i5 support 2133Mhz? Anyway that's not a big fuck up. Ram will work at 2133Mhz mode then.
That would depend on the motherboard if it can down clock the RAM to run at 2133 MHz. Typically the faster memory speeds are only supported by the higher end processors, like the i3-i7. Buying faster RAM than you're CPU supports can cause compatibility issues.
https://bitcointalk.org/index.php?topic=2730770.msg27954939#msg27954939