What Deficiency does the below rebus represent?

VIT_MIN

What is black when you buy it, red when you use it, and gray when you throw it away?

Can you identify the Oscar-winning movie from the rebus below?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

Can you spot what's wrong with the following sentence?

PETER WAS ANGRY AT
HIMSELF BECAUSE HE
ACCIDENTALLY LEFT THE
THE KEYS TO HIS CAR
AT HIS FRIEND'S HOUSE.

Here is a mathematical expression that also secretly tells a movie name. What movie is that?

There was once a troop of 5 elves. The 5 elves were very dedicated on finding the magical treasure of 1000 coins. However, being elves, they were super geniuses, very greedy and they did not hesitate in taking lives of other elves. The 5 elves were named Aye, Bee, Cee, Dee and Ee, ranked from high to low respectively, from Aye to Ee. One fine day, their efforts brought results and they found 1000 coins. Now they had to split it in between them as per their ranks. The lowest ranked elf has to make the proposal. If the proposal is accepted by majority, it is agreed, or the suggesting elf is killed.

What proposal should elf Ee make ?

They are three errirs in this question. Can you find them?