In a sense, no, because the meter is now defined in terms of the second and the speed of light. But you can still do all the same experiments that people used to do to measure the speed of light; it’s just that now they’re effectively experiments to measure the length of the meter. Fundamentally, nothing has changed; it’s just a change in how we label things.
The various buttons on a computer to reboot and power it off are generally run by some low-level embedded software running on the motherboard. When they are pushed, they activate a reset sequence.
It is possible to screw things up sufficiently that even this low-level system stops working correctly, and you have to do a hard power cycle to get things back up and running. It’s also possible in a few rare cases to screw things up so bad that you cause actual damage to the hardware.
I just assumed the “reset” was a glorified RC circuit to the CPU reset; but we were too lazy to find a schematic and actually check it out.