Solution:

One of 57620 or 57628 must be the secret code.

Explanation:
Hint-1: 79314
Only 7 is there and in wrong

Hint-2: 95643
6 is in the right position while 5 is not

Hint-3: 57319
5 and 7 are in the right position

Sum Hint: A + B + C + D + E = D*10 + E
CaseA - 57620
5 + 7 + 6 + 2 + 0 = 2 * 10 + 0
20 = 20

CaseB - 57628
5 + 7 + 6 + 2 + 8 = 2 * 10 + 8
28 = 28

Solution:

CANNOT BE CRACKED

Explanation:
This code can be cracked with the help of table below.
i.e
31 => 3rd row and 1st column => C
11 => 1st row and 1st column => A
33 => 3rd row and 3rd column => N
and so on....

Solution:

8m

Explanation:
From green bar, it's clear that
the height of vertical bar = 2/3 of uninterrupted shadow length

Therefore shadow of 6m of red bar indicates the height of 4m.
The remaining red bar casts a direct 1:1 vertical projection on the wall.

Therefore total length = 4m + 4m = 8m.

Solution:

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

Solution:

888

Explanation:
Part-1: Triangle
The triangle is an equilateral triangle.
The value of E and L is determined by the position in the English alphabets i.e E = 5 & L = 12. Together they form number 512

As we know that the equilateral triangle has 3 equal sides, therefore
X^3 = 512
X = 8
=> XXX = 888 ... (desired)

Part-1: X/3 = X
X is the 24th letter, therefore 24/3 = 8

Solution:

Grid 5.

Explanation:
If you arrange the images as shown in the below image, you will notice that they all are connecting images.

Solution:

Rashid's son-1: 1 11 21 31 41 51 61 71 81
Rashid's son-2: 2 12 22 32 42 52 62 72 73
Rashid's son-3: 3 13 23 33 43 53 63 64 74
Rashid's son-4: 4 14 24 34 44 54 55 65 75
Rashid's son-5: 5 15 25 35 45 46 56 66 76
Rashid's son-6: 6 16 26 36 37 47 57 67 77
Rashid's son-7: 7 17 27 28 38 48 58 58 78
Rashid's son-8: 8 18 19 29 39 49 59 69 79
Rashid's son-9: 9 10 20 30 40 50 60 70 80

Solution:

73

Explanation:
It's a very famous puzzle known as "Josephus Problem Puzzle". It can be solved in various ways but the trick to solve this problem is illustrated below.

Binay number of 100 is: 1100100
complement pf 100 is 0011011, whose decimal equivalent is 27.
The desired answer will be 100 - 27 = 73

Solution:

A = B = K =6
C =7
D = H = 1,
E=0 ,
F = I = G = 4,
J=3,
L=5

Now we can rewrite the equations as :
66 = 76 - 10
44 = 60 - 14
16 = 64 - 46
37 = 67 - 30
35 = 53 - 16
10 = 74 - 64

Solution:

Sucre : 1 cupcake
T-Bag : 2 cupcakes
Burrows: 3 cupcakes
Scofield : 5 cupcakes

Explanation :
It's obvious if the prisoner has eaten 5 or more cupcakes than he will not ask this question "did you had more cupcakes than me?" as it will make him the person who had eaten maximum cupcakes.
A) Sucre : Must not have eater 5 cupcakes, therefore he has eaten anywhere between 1-4 cupcakes.

B) T-bag : Since sucre asked him the question T-bag knows sucre have eaten between 1 - 4 cupcakes, and therefore he must have eaten 2 to 4 cupcakes(it can't be 1 else he will reply answer as "No".)

C) Burrows : Replied with the answer as "I don't know and based on logic B) he knows T-bag must have eaten at least 2 and he replied no which implies that he must be eaten 3 or 4.

D) Scofield replied he know all, which indicates he must have eaten 5.
Therefore cupcake division is as below:
Sucre : 1
T-Bag : 2
Burrows: 3
Scofield : 5