Solution:

Newspaper delivery man was the murderer because of absence of Wednesday and Thursday missing newspaper.
This indicates he already know that there is no one to read it.

Solution:

Dabid is the killer

drawing room(D) , art room(a) , bed room (b) , ice-cream room (i) , desk room (d)

Solution:

Frost forms on the inside of the window, not the outside. So shweta could not have wiped it off to discover Mr.Ankit's body.

Solution:

mother

We know from (3) that the youngest person was not the victim, from (4) that the youngest person was not the helper and from (6) that the youngest person was not the killer. The youngest person can only have been the witness therefore. If we make up a chart there are now three possible combinations:

Oldest person (father) H H M

Next to oldest (mother) V M H

Next to youngest (son) M V V

Youngest (daughter) W W W

(H = Helper ; V = Victim ; M = Murderer ; W = Witness)

We can work out from (5) that the father was the oldest, from (2) that the youngest person must have been the daughter. Therefore the next to the youngest must have been the son and the next to the oldest, the mother.

Solution:

Mark Benson '?' = question MARK, so the note on the door reads 'Question Mark Crimson broke your window.'

Solution:

Jason Kumar

The number on the calendar was written in a hurry.Sherlock matched the written number with the months of the year.
So the B was an 8, thereby giving us 7-8-9-10-11: July, August, September, October, November.

Use the first letter of each month and it spells J-A-S-O-N.

Solution:

Bill. If you read the message upside down, you'll notice that the numbers resemble letters and that those letters form legible sentences. The message is 'Bill is boss. He sells oil.'

Solution:

1)The first bit is easy, as the first letter of each plate spells WHODUNNIT IX(A challenge to our Detective.)
2)The second bit is a little trickier, but I gave you the solution.If you read the last three letters in each plate from the bottom up and right to left you get ADVANCE EACH LETTER BY THE NUMBER SHOWN, so advance W by 5 to get B, H by 13 to get U and so on until you spell BUTLER DID IT.

Solution:

The wife was about to have a baby. They were driving to the hospital. The baby was born, and the wife didn't survive the birth

Solution:

At that moment, the time, and day could be written as '12:34 5/6/78'