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Say I have a unit consisting of: A Wolf Lord on a Thunderwolf (cavalry), 3 TWC (cavalry), a Rune Priest on bike, a White Scar Captain on Bike, 2 Fenrisian Wolves (Beasts) and a a Wolf Priest on a bike. Do the White Scars still have Hit and Run? Do the Space WOlves still have Counter Attack and Acute Senses? can the Fenrisian Wolves reroll charge distances? Who has HoW?

Generally, special rules themselves are not transferred between the models of a mixed unit, but they sometimes still benefit from them.
Breaking down your examples (in no particular order):

Hammer of Wrath - "If a model with this special rule..." only the models in the unit that have HoW (and make it into B2B) get the bonus hit.

Fleet - "A unit composed entirely of models with this special rule..." though the Beasts have Fleet, because the whole unit does not have it, none of them benefit.

Acute Senses - "If a unit contains at least one model with this special rule..." & Hit and Run - "A unit that contains at least one model with this special rule..." because the unit contains even a single model with the rule, the whole unit can benefit from it.

Counter Attack - Now, this is the red-herring one. It begins "If a unit contains at least one model with this special rule..." making us think it might affect the whole unit, but if we keep reading we get "...every model with the Counter-attack special rule in the unit gets +1 Attack...". So any unit containing a single Counter Attack model triggers the effect (since units get charged, rather than models), but only models with the rule actually benefit.

The real problem is attacks with Preferred Enemy, Monstrous Hunter or the likes.