Learn English – ‘Would have known’ vs ‘could have known’

If you had told me, I would have used the other route.
If you had told me, I could have used the other route.

Would here denotes a certain consequence of the unreal condition: no question about it, I would have used the other route.

Could denotes a possible consequence of the unreal condition: if you had told me, I might still have taken this route but I would have had the choice of taking the other route.

If you had told^{Past Irrealis} me, I would^{Present Irrealis} use the other route.
If you tell^{Present Realis} me, I would^{Present Irrealis} use the other route.

These are not quite impossible, but the circumstances under which either would be acceptable are very unlikely to arise. Ordinarily these forms would be understood as having the tense/mode significances I have noted in superscript, and in most cases the two verbs, the one in the IF clause and the one in the THEN clause, should have the same tense and mode.^†

^† This is not always the case in conditional clauses involving logical inference; but I do not think either of these sentences can be read as inferential.

The "have had" construction is the present perfect form of "to have". As with other verbs, the present perfect describes either an ongoing condition,

He has had that car since he was a teenager.

or a life experience:

In my life I have had many good dinners.

Adding "could" or "would" to this is no different from other uses of could (to describe potential) or would (to describe a hypothetical).

He would have had that car since he was a teenager, if he hadn't driven it into the lake last week.

In my life I could have had many good dinners, if I was a better cook.

It's not a common construction, and it's not important to use it. Usually these kind of sentences can be written using the simple past:

He had that car since he was a teenager

I had many good dinners in my life.

Remember that to use the past perfect of "to have", you have to start with an example that correctly uses that verb. For example:

That building has a good address.

That building has lots of tenants.

That building has ongoing construction.

Then you can change it to the present perfect:

That building has had a good address (but ...)

That building has had lots of tenants (but ...)

That building has had ongoing construction (but ...)

And then add could/would as appropriate.

That building would have had ongoing construction (if it wasn't raining).