Solve below rebus puzzle?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

In a jungle where there are no street lights or any other artificial source of lights, I notice a black snake crossing the road.
How did I get sight of the snake?

Count the number of lines in the image below ?

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

John is found dead in a bare field. Nobody killed John,
John did not commit suicide.

Inspector Jacob found a bag just a few meters away from John which could save his life. What was in the bag?

Replace the question mark with the correct number, given the pair of numbers exhibits a similar relationship?

? : 3839 :: 11 : 1209

What goes up but never comes down?

There was a minor accident with a doctor's son but the doctor noticed no major injury. After the treatment, the father of that doctors son is sitting with the son of the doctor without the doctor being in the room.

How can this be possible?