QUESTION 4:

The size of the square is of size 10. So assuming zero indexing,
vertical side1 (column Index = 5): row index from 5 to 14
vertical side1 (column Index = 14): row index from 5 to 14
horizontal side1 (row Index = 5): column index from 5 to 14
horizontal side2 (row Index = 14): column index from 5 to 14

Note:
while indexing, data_new[a:b,c] denotes,
row index: a to b-1
column index: c

Similarly data_new[a,b:c] denotes,
row index: a
column index: b to c-1

Code:

import matplotlib.pyplot as plt
import numpy as np

size_1 = 20
size_2 = 20
data_new = np.random.random((size_1,size_2))

data_new[5:15,5] = 4
data_new[5:15,14] = 4
data_new[5,5:15] = 4
data_new[14,5:15] = 4

fig = plt.figure(figsize=(10,10))
plt.imshow(data_new)
plt.colorbar()
plt.show()

OUTPUT:
https://ibb.co/q7ZvVRh