Solution:

The person is leaving hospital after visiting his wife. His wife is on a life support system. The elevator has stopped due to the power cut. If there was an emergency backup generator functioning well, the elevator would have also be running. It stopped in between means that the life system support has stopped as well.

Solution:

If the man killed himself, he would not have been able to rewind the cassette. Thus it is clear someone else killed him.

Solution:

Kid1, he was left with one rock.

Solution:

smoke inhalation

Solution:

The youngest son went over and blew out the candle after Death left because the son said 'till the candle wick burns out', not 'till the candle burns out'.

Solution:

Hhe hung herself using big Ice slabs , which are now now melted and hence puddle of water.

Solution:

Tanu was blind and she was reading book by Braille.

Solution:

Youssef is name of a man , and out of 11 people only one is male

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:

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.