Solution:

Newspaper delivery man was the murderer because of absence of Wednesday and Thursday missing newspaper.
This indicates he already know that there is no one to read it.

Solution:

What is the correct time ?

Solution:

There are 3 fruits (1 grapes, 1 apples, and 1 oranges).

Solution:

Four

three placed flat on the table in a triangle(touching each other) and put the fourth one on top of them in the middle.

Solution:

Six.

There are only five colors, so six socks guarantee that two will be the same color.

Solution:

Kid1, he was left with one rock.

Solution:

The Stars

Solution:

Put one black rock in one sack and put all the rest in the other one. In such manner you will get about 3/4 probability of surviving.

Solution:

457730 * 4 = 1830920
(DOLLAR * 4 = QUARTER)

Solution:

Old password : altered

New Password : distinct

Solution:

The three errors are as follows:
a) fynd is spelled wrong. The correct spelling is 'find'.
b) that is not appropriate to use here. It should be 'this'.
c) There are only two errors in the question and that is the third error because the questions asks us to find three.