Solution:

At that moment, the time, and day could be written as '12:34 5/6/78'

Solution:

Milk.

Explanation:
The cream comes to the surface and hence milk is heavier than cream.

Solution:

Mount Rushmore (4 men faces carved into Mount Rushmore)

Solution:

Discovered or not, it's always biggest ocean in the world.

Solution:

The dead guy is Superman. He died because he was exposed to a Kryptonian rock.

Solution:

Mitch and Irene are the names of hurricane occurred in 2011 and 1998 respectively.

Solution:

Snail (snail foot is a muscle that allows it to move)

Solution:

"EUNOIA" is the shortest(length-6) word that comprises of all vowels.
But many dictionaries does no include this word.

So next comes many seven letter words that contain all vowels.
* SEQUOIA,
* EULOGIA,
* MIAOUED,
* ADOULIE,
* EUDOSIA,
* EUNOMIA
* EUTOPIA
* MOINEAU
* DOULEIA.

EUNOIA means "alertness of brain"

Solution:

It is possible. You have to build a house at south pole and then, all the walls will face the north direction.

Solution:

The required word is Buffalo.

Buffalo is a noun that refers to an animal. However, it is also a verb that means 'to bully'. Let us see how it can be used.

Sentence: Buffalo.
Meaning: Go and bully someone.

Sentence: Buffalo buffalo.
Meaning: Animals bully.

Sentence: Buffalo buffalo buffalo.
Meaning: Animals bully other animals.

Sentence: Buffalo buffalo buffalo buffalo.
Meaning: Animals that are bullied by other animals, in turn, bully other animals.