In the given code, A = 2, B = 4, C = 6,.... , Z = 52.

So, ACT = 2 + 6 + 40 = 48 and

BAT = 4 + 2 + 40 = 46

Justification:   

In statements A and B, the common code word is 'na' and the common word is 'water'.

So, 'na' means 'water'.

In statements B and D, the common code word is 'jo' and the common word is 'life'.
So, 'jo' means 'life'.
Thus, in statements B, 'tod' represents 'is'.

The letter of the word are written in a reverse order and then each letter is moved one step backward to obtain the code.

The first, second, third, fourth, fifth and sixth letters of th word are respectively moved two, three, four, five, six and seven steps forward to obtain the corresponding letters of the code.

Z C o d e ? 26 ? 26 2 ? 13 ? 13 3 = 2197

$$\begin{gathered} R C o d e ? 18 ? 18 2 ? 9 ? 9 3 = 729 \\ \end{gathered}$$

Similarly,  J C o d e ? 10 ? 10 2 ? 5 ? 5 3 = 125

 The alphabets are coded as shown :

$$\begin{gathered} R O S ? E C H A I P \\ 6 8 2 1 7 3 4 5 9 \end{gathered}$$

So, in SEARCH,

S ia coded as 2,
E as 1,
A as 4,
R as 6,
C as 7,
H as 3.
Thus, the code for SEARCH is 214673

Justification:      

We can find the code for 'home' from the second and third statements.

For finding the code for 'they', we need the code for 'go' which cannot be determined from the given data.
Clearly, statement A is not necessary.

The letter is the first half and the letter half of the word are separately reversed to obtain the code.

The colour of clean sky is 'blue' and as givne, 'yellow' means 'blue'.

so, the colour of clear sky is 'yellow'.

The colour of clear sky is 'blue' and as given, 'blue' is called 'sky'.

So, the colour of clear sky is 'sky'.