The alphabets in the given words are coded as follows :

$$\begin{gathered} M ? I ? S ? T ? A ? K ? E N D \\ 9 7 6 5 4 1 2 8 3 \end{gathered}$$

D is coded as 3,

I as 7,
S as 6,
T as 5,
A as 4  and
N as 8.
So, the code for DISTANT is 3765485.

From the given information :

how can you go = ja da ka pa....(1)
can you come here = na ka sa ja...(2)
come and go = ra pa sa....(3)
from (1)&(2), can you = ja ka...(4)
from (2)&(3), come = sa...(5)
Using (4)&(5) in (2), we get here = na.

From the given information :

D O W N A M E == 5 @ 9 # 6 % 3
MODE = %@53

Justification:      

In the first and second statements, the common code digit is '8' and the commmon word is 'good'.

So, '8' means 'good'.
In the first and third statements, the common code digit is '1' and the common word is 'fruit'.
So, '1' means 'fruit'.
Thus, in the first statement, '5' means 'sweet'.

AS HARD is coded as "1357" and SOFT is coded as "2468"
So H is coded as 1, A as 3, R as 5, D as 7
and S as 2, O as 4, F as 6, T as 8

Now in 21448, go number by number
2 is the code for S
1 is the code for H
4 is the code for O
and
8 is the code for T

hence, 21448 will stand for SHOOT

ja ke mo pe    =>  at a frog's leap          --------(i)

mo la ki so     =>  take a leapahead       --------(ii)

re bo na ja     =>  insects are frog's diet  --------(iii)

From (i) and (ii),   a leap  =>  ki mo       --------(iv)

From (i) and (iii),  frog's   =>   ja           ---------(v)

From (i), (iv) and (v),  'at' => pe

Look at the following table which shows the letters and their respective codes :

Letter     A     B     D     E     G     I     M     U     

Code       5     8     3     2     4     1     7     9

Therefore, the code for IMAGE is 17542

The letters at odd positions are each moved two steps backward and those at even positions are each moved two steps forward and the obtained code is reversed to get the corresponding letters of the code.