A:Answer No, DDR4 and DDR5 ram have different pins, the two are not physically compatible. You can't insert DDR5 ram into a slot made for DDR4 ram without physically damaging the RAM, slot, or both.
You might be able to find some desktop motherboards with slots for both, but they will run only one type at a time. That's how they did it when DDR 3 first came out, and DDR4.
I highly doubt you will ever find a laptop that accepts ddr4 and ddr5