What does this below rebus puzzle mean?

I know a ten-letter word in the English language which can be typed using only the top rows of the computer keyboard.

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

Which is faster, Heat or Cold ? Explain.

Two men are in a desert. They both have packs on. One of the guys is dead. The guy alive has his pack open, and the guy who is dead has his pack closed. What is in the pack?

Baseball bat and ball cost $100. If the bat cost $99 more than the ball, what is the cost of each?

I have holes on the top and bottom. I have holes on my left and on my right. And I have holes in the middle, yet I still hold water. What am I?

Intelligence Agency need to break the vault but the problem is that they are not able to break the vault.

On the vault, a text is written as:

31 11 33 33 43 45
21 25
31 24 11 31 51 41

To Break the code Intelligence Agency brings a mathematician named Joseph.
Minutes later he deciphers the code.

Whats the code?

I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

Using mathematical symbols like +, -, and x in order to make the equations correct. Replace # with the above-given symbols.

9 # 8 # 7 # 6 # 5 # 4 = 91