Solution:

Starting with the first two words, Take the first and last letters, reading from left to right. Example: Carrot fiascO "from these pairs" the message is as follows:

CONGRATULATIONS CODE BREAKER

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:

The code word is TIE.

Let us assume that the word is MOD. Now if you are told one character of this word, you would not be able to identify the number of vowels in the word. For example if you are told M, then the word can be MOD or AIM but they both have different number of vowels. If you are told about O, then there are two words MOD and OAT which again have different number of vowels. If you are told about D, there are two words again MOD and DUE which have different numbers of vowels again.

In such manner, all the words that have M, O or D in them can be excluded. Then only word that remains is TIE.
If you are told about T, there are two words OAT and TIE which both have two vowels.
If you are told about I, there are two words AIM and TIE which both have two vowels.
If you are told about E, there are two words DUE and TIE which both have two vowels.

Thus TIE is the code word.

Solution:

7, 4, 6, 5, 8

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 clerk said that every day the password is CHANGED. Changed is the password.

Solution:

I(1) + ate(2^3 is 8) + Some(Sum symbol) + Pie(Symbol)
= I Ate Some Pie and It Was Delicious

Solution:

1. 26 L of the A (26 Letters of the Alphabet)

2. 7 D of the W (7 days of the Week)

3. 1000 Y in a M (1000 years in a millennium)

Solution:

1. 8P of the SS - 8 planets of the Solar System
2. 1M of the E - 1 Moon of the earth
3. 1S of the SS - 1 Sun of the Solar System
4. 60M in 1H - 60 minutes in 1 Hour

Solution:

Just In case