Usage of simple future and future perfect with static and dynamic verbs

Question

Please look at the following sentences

1. We'll be home by midnight.

2. We'll have been home by midnight.

If we use 'be home' in the sense of being present at home and according to the definition of 'by' which is either 'before' or 'at', then is it not possible that we may not be home at midnight but an hour before midnight, if we used by in the sense of before?

Also, I find the meaning of the sentence change with static verbs when we use simple future and future perfect. Does the meaning of the sentence change when we use a stative verb in simple future and future perfect? Just like the midnight example above unlike with dynamic verb?

Editing in response to Alan sir's advice

In 'By the time I reached, he had arrived'. Does this mean he was there when I reached or it doesn't specify that and probably he may have left moments before my reaching home? It is only the context that may tell us what was true at the moment of my reaching there. He could have left also, but, 'by the time' does not say that. Am I right?

Like, for example

In 'By the time we met him not only had he become sick from flu, but also he had recovered from it, so he was healthy'.

Is the above sentence correct and logical? Can we use 'by the time' in the above manner?

I mean does 'By the time X, Y, Z' does this construction have a relevance at the time of X? Does it always mean at the time of 'X', Y and Z are still true?

Like, for example

'By the time I went home, he had left for school, but had also arrived moments earlier than I reached'.

Thanks.

Answer 1

First, by means you'll be home by midnight at the latest, so yes, it could mean you'll actually be home at 11pm or actually any time up to and including midnight.

EDIT in response to comment:

What you are doing is informing someone of the latest time that you will be home, so that if they arrive at midnight you will be home.

We do not use either

We'll be home by midnight

or

We'll be home before midnight

to mean

We may be home earlier than midnight, say 11pm, so at midnight we might not actually be home.

This is the result of applying logic to language, and language use does not work that way, at least not all the time (double negatives in English are often used for emphasis, not to cancel each other out).

And yes, the meaning of the sentence changes when you switch from will be home to will have been home, just like it changes when you switch from will arrive home and will have arrived home. The future perfect talks about the present situation from the point of view of future time. Let's look at the two:

We'll be home by midnight.

is basically a present promise that refers to future time.

We'll have been home by midnight

talks about the "present situation" in the future. Consider

We'll have been home by midnight when Sam finally gets there.

This means that at whatever future time you are actually home (which time is by midnight), you will already be home at that future time when Sam gets to your home. It's not a construction that will be used often, but it's grammatical and it does differ from the use of will be home (what you have called the simple future).