1.) Your examples seem grammatical in terms of tense (note at bottom on typo). Depending on context I might use a modal form (e.g. "Everything must be spotless") but I see no issue with using simple perfect.
2.) If you're asking whether you should use future perfect in the first example, note what that changes:
Everything will have been spotless by the time they get here.
In the first example, everything may not be spotless in the present but it will be by the time they arrive. In the future perfect version, everything may not be spotless in the present, but it will be for some period of time before the time they arrive. Future perfect is used to look backwards from some point in the future. That seems awkward unless you're emphasizing an earlier completion time. Here's that example with added context:
Guests are due to arrive at 6:30, but I will be done cleaning by 5. So everything will have been spotless by the time they get here.
Unless you specifically want to emphasize an earlier time, future perfect seems unnecessary here. This sentence would still convey the information that everything will be spotless in time:
Guests are due to arrive at 6:30, but I will be done cleaning by 5. So everything will be spotless by the time they get here.
The future simple signals the logical consequence of being done cleaning before the guests arrive.
3.) No, I don't see the difference between a state and an action affecting whether you should use future simple or future perfect tense. Instead it's functioning more on context and on whether you're emphasizing a future event or an event in the past from the perspective of the future.
(note) But check out "Nobody will even see you hair" in your second example. Do you mean "your hair?" "you there?" Something else?