Four-digit numbers are to be formed using the digits 1, 2, 3 and 4; and none of these four digits are repeated in any manner.

Further,

1. 2 and 3 are not to immediately follow each other

2. 1 is not be immediately followed by 3

3. 4 is not to appear at the last place

4. 1 is not to appear at the first place

How many different numbers can be formed?