Your CPU is capable of running >2400 MHz RAM, but it's considered an overclock, so it's only possible with a Z170/Z270 mobo. This is true of every Skylake/Kaby Lake CPU as far as I know.
G4600 is a low end CPU and the normal thing would be to pair it with a cheap mobo B250 and a RAM of 2400 (because with B250 it can not really exceed 2400). If you are using a Z270 mobo and 3200 memories you are wasting money because G4600 does not It can overclock and only get an insignificant advantage with 3200 memories.
On the other hand you will only get the 3200 if you activate XMP in your mobo. If it does not, the memories will run at the spd speed of your memory.