What does this mathematical rebus means ?

Two boys wish to cross a river. The only way to get to the other side is by boat, but that boat can only take one boy at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both boys manage to cross using the boat.

How?

I am the beginning of the end, and the end of time and space. I am essential to creation, and I surround every place. What am I?

A number can be multiplied by multiple of nine
i.e 9 18 27 36 45 ...

and the resulting number consist of only one digit.

Can you identify the number ?

What four weights can be used to balance from 1 to 30 pounds?

Identify the 10 differences between the two given pictures.

Can you find out the remainder when 3^300 is divided by 5?

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

Who am I?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

John walks into the daily grocery shop and steals a $100 bill from the shop. An hour later John returns to the shop and buys some daily products for $40. John pays the owner the $100 bill and therefore the owner returns him $60.

How much money did the owner lose?