What does this rebus means ?

PROG WORKRESS

Which digit occurred maximum times between the number 1 and 1000?

What does it mean?

I am written with two letters.
I said with the one.
I usually am seen with the two.

Who am I?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

There is a brick of gold and a brick of iron in a boat (both 10-inch blocks), if they are both dropped into the water which will make the water level higher?

You throw me out when you want to use me and you take me in when you don't want to use me.

Who Am I?

Can you find the missing number in the third row?
35 20 14
27 12 18
5 2 ?

John can place six large boxes or nine small boxes into a carton.

Can you find out in how many cartons can he place sixty-six boxes in total?

I am Huge on Sunday and Saturday.
I am small from Tuesday to Thursday.
I do not exist on Monday and Friday.
Who am I?