investigate the function unescape()

what the imput string here? a=a%26b%3Dc%3F ?

Read the description more carefully. It says:

• Make sure you decode the URI components correctly

You did not decode the URI components.

You are meant to divide each the box of 9x9 into sub-boxes of 3x3. You are only meant to have each number once in each column, line and sub-box. You are only meant to have each number once in each column, line and sub-box. However the numbers 1, 2 and 3 all appear 3 times instead of once and 4-9 appearing once as well.

From @myjinxin2015:

each sub 3x3 matrix should be 123456789

1 2 3 | 4 5 6 | 7 8 9
2 3 1 | 5 6 4 | 8 9 7
3 1 2 | 6 4 5 | 9 7 8
------+-------+------
4 5 6 | 7 8 9 | 1 2 3
5 6 4 | 8 9 7 | 2 3 1
6 4 5 | 9 7 8 | 3 1 2
------+-------+------
7 8 9 | 1 2 3 | 4 5 6
8 9 7 | 2 3 1 | 5 6 4
9 7 8 | 3 1 2 | 6 4 5

From @bkaes:

The first box

1 2 3
2 3 1
3 1 2

invalidates the third Sudoku rule.