Solution:

Number 3

Explanation:
Since it's a ladies bathroom, so only ladies can enter the bathroom and hence most likely the killer.

Solution:

Rooster doesn't have webbed feet.

Solution:

It can be done as shown in the picture below. Key to solving such problems is to fill the prime number first.

Solution:

yaM

Explanation:
voN luJ ? raM beF

Step-1: Reversing the input text gives us:
Feb Mar ? Jul Nov

Step-2: Replace by month numbers
2 3 ? 7 11

Step-3: Find the relation
They all are prime numbers, the missing number here is "5".

Step-4:
5th month is May and reverse of May is yaM (answer)

Solution:

3

Explanation:
Possible matches
Chelsea vs Tottenham
Chelsea vs ManCity
Chelsea vs Arsenal
Chelsea vs Liverpool
Tottenham vs ManCity
Tottenham vs Arsenal
Tottenham vs Liverpool
ManCity vs Arsenal
ManCity vs Liverpool
Arsenal vs Liverpool

Therefore there is a total of 10 matches. After every match, 2 points were distributed between two teams as:
Case1: One of team wins:
Winning team will get 2 points.

Case2: Match ends up in a draw
Both teams will share a point.

Therefore 10*2 = 20 points should be the sum of all team points.

6 + 5 + 4 + 2 + ? =20
? = 3

Solution:

Turn the equation to 180 degrees (upside down)

16 = 8 + 8.

Solution:

They are matched as shown in the picture below.

Solution:

Zouma is 3 and has two footballs.
Ake is 1 and has one football.
Kalas is 4 and has three footballs.
Aina is 2 and has four footballs.

Solution:

The node can be connected as shown.

Solution:

8/(1−1/5)