The murderer is Fred.

Andy is the seer so exclude him.
Now, if Brian was murderer, then Chris should have been killed.
Now we know that Chris was blocked. Therefore he cannot be the murderer.
Daniel cant be the killer as he was killed himself.
This leaves with Fred.

The suspicion was natural. If the man thought the room was his, he would have tried the keys and not knocked on the door.

The word “World War I” could not have been engraved on the sword. This is because the Second World War had not happened then and nobody knew that it will happen.

All (all months have 28 days at-least)

The word is “Buffalo”.

According to the dictionary meaning, Buffalo is a noun meaning an animal. It is also a verb meaning “to bully”.

Sentence: Buffalo.
Meaning: Go and bully someone.

Sentence: Buffalo buffalo.
Meaning: Animals bully.

Sentence: Buffalo buffalo buffalo.
Meaning: Animals bully other animals.

Sentence: Buffalo buffalo buffalo buffalo.
Meaning: Animals that are bullied by other animals, in turn, bully other animals.

The missing number is 19.
Let us label the boxes with Rs and Cs where R refers to the Row number and C refers to the Column number.

Now,
R4C1 = (R1C1 * R3C1) -R2C1 = (5 * 2) -8 = 2
R4C2 = (R1C2 * R3C2) -R2C2 = (7 * 4) -10 = 18
R4C3 = (R1C3 * R3C3) -R2C3 = (6 * 5) -12 = 18
R4C4 = (R1C4 * R3C4) -R2C4 = (4 * 9) -17 = 19

A = 1, B = 2, C = 3….

DEAD = 4 + 5 + 1 + 4 = 14
BALL = 2 + 1 + 12 + 12 = 27
FEAR = 6 + 5 + 1 + 18 = 30
SHOP = 19 + 8 + 15 + 16 = 58

Now, 14 < 27 < 30 < 58

Therefore, the order
DEAD, BALL, FEAR, SHOP

The missing letters are H and L. The word is Avalanche.

The next number is 15.
In the given series, there is actually a pair of series. Pick the alternate digits.
One series is:
0, 1, 2, 3, 4, 5
Here the digits are progressing by one.

Second series is:
0, 3, 6, 9, 12, _
Here the digits are a multiple of 3. Therefore, the next number will be 15.

The missing letters are C (on the right) and P (on the left) and the word is champion.