The key explains that when using the phrase "abide by" you must ensure that "a person" serves as the subject of the sentence. Is that true?
a obey ... b abide by ... c comply with ... d observe
Pictures are always useful...
As suggested by Řídící, at least part of the reason abide by, observe, obey rarely occur in such contexts is because those verbs are more strongly associated with deliberate actions by sentient subjects.
But part of the reason is just "established custom & practice". I'd also add that formal legal contexts are more likely to favour compliance (with laws) as opposed to formal religious contexts where you'll more often see references to observance (of rituals and rites).
It's really just preference, though - there's no absolute principle of vocabulary or syntax requiring or debarring any particular verb form in such contexts, so it's misleading to present this as "test material" with right and wrong answers. It would be pedantic in the extreme to complain about, for example,...
There are various mechanisms for making sure that administrative actions abide by due process and are explicitly justified
Can “comply with” here be replaced by “abide by”?
No, because:
The key explains that when using the phrase "abide by" you must ensure that "a person" serves as the subject of the sentence. Is that true?
Yes, I think that makes sense. Abide by means something like accept and follow, where acceptance is a mental state of sorts. Activities have no mental state. It has to be some person (or group or entity or maybe a smart animal or perhaps even something like a philosophy etc.) that does the accepting, and thus the abiding.
