Depends on brands I guess. Although you might have a failure test in house before shipping. Also a lot of manufacturers actually keep the gear on standby all the time, eventhough there's a switch. It's just a mute.
Nope, the results from the dac chip itself are an approximation, that's the way the Delta-Sigma process works. Oversampling is a trick used to reduce the range of the approximation, but it's still inaccurate, only to a lower extent.
How about you read the thread from the beginning and try to understand where the OP is coming from ? This thread started as pcm vs dsd, not sd vs r2r. Even Currawong said it.
How about trying to get an idea how DAC chips actually work, and the radical difference between the mathematical results of each chip ? You must know that DS chip actually approximate their results which means that they are inherently innacurate right ? Are you familiar with the GiGo principle in...