FMUv3 issue with pixhawk 2.4.8

I recently got a pixhawk 2.4.8 from aliexpress.

I tried to use FMUv3 but still can’t find SYS parameter to enable.

Is this pix only FMUv2 able?

I see the different is 1M or 2M ram

Will this make a big difference for usual hobbyist?