What does this below rebus puzzle mean?

Given that

(78)^9 = 6
And (69)^4 = 11

Can you find out

(99)^2 =?

(Note: This is Logical, not Mathematical)

Forwards I am heavy, backward I am not. What am I?

It's a test that will check your IQ.

Suppose you have one 11 minute hourglass and one 13 minute hourglass.

Can you measure exactly fifteen minutes using them ?

In particular commonwealth games, a female participant won silver and gold medals for a single event.

How can this be possible?

If eleven plus two equals one, what does nine plus five equal?

In the below-given picture of a pretty girl, there is something wrong. Can you find out what it is?

I cannot talk, but I always reply when spoken to. What am I?

John is pretty weird. He likes toffees but hates chocolates. He loves books but never reads. He likes to build his troops in an online game but does not proceed with the war. He likes to go swimming but is afraid of water.

Seeking this behaviour, can you tell whether he likes balloons and parties?

There is an English word that can be used up to four times in a row without modifying the spelling and form a valid grammatical sentence.

Do you know what word is that?