Cool number property!

Try this out!
Take any four digit number such that all the digits cannot be the same. Eg; 9813,2221,5573 is possible but not 1111,2222...
Now rearrange this number so that the larger digit is first then smallest is the last;
let say 5573, so 7553.
Then arrange the smallest digit first then largest digit last, so 3557.
Take the larger number form and deduct it with the smaller number form,
i.e, 7553 - 3557 = 3996
Do it same for the number formed, i.e, 3996, and keep doing so,
i.e, 9963 - 3699 =6264
6642 - 2466 =4158
8541 - 1458= 7083
8730- 378= 8352
8532 - 2358= 6174
7641 - 1467 = 6174
Try it with any other 4 digit number that the digits are not all the same and it will always reach 6174!

Puzzle i created.

Here's a puzzle i created out of boredom:

Let's call a diagram "dots and lines" if it follow this rules:

1)a dot is literally a dote and line is literally a line.

2)a dot must be connected to a line. Also a line must be connected by only two distinct dots.(Meaning a pair of dots can only have one line connecting them together.)

3)Any region formed can only be bounded by at most three lines.

4)One line cannot intersect with another line.(If the point of intersection is a dot, then the intersection is allowed.

Here's the puzzle.

Level 1: Draw a "dots and lines" diagram with the minimum number of dots such that each dots only have 1 line connected to it.

And generally, level n:Draw a "dots and lines" diagram with the minimum number of dots such that each dots only have n line connected to it. Where n is an integer.

So what is the highest level you can go to? Post your answers if you want to :D.

Possible "dots and line diagram":

Here are incorrect diagrams:

Please click to see the comments on why they are wrong.