The Riddle Answers!

Here are some riddles that you have to answer! 16

06
68
88
?
98

What is the ‘?’?

Many have heard me, but nobody has seen me, and I will not speak back until spoken to.
What am I? 

Alone I am 24th, with a friend I am 20.
Another friend and I am unclean.
What am I?

When is 99 more than 100?

A window cleaner is cleaning a window on the 25th floor of a skyscraper when, suddenly, he slips and falls. He has no safety equipment and nothing to soften his fall, and yet he is not hurt. How can this be?

1
11
21
1211
111221
312211

What is the next number in the sequence?