Are these sentences ok?

[rainyday]

1) Write legible.

2) Improve your handwriting.
3) hand writing can be improved.

4) work on the formation of the letters.

5) Don't cut the line ( queue).

[emsr2d2]

1) Write legible.
Write legibly.

2) Improve your handwriting.
Fine.

3) hand writing can be improved.
Handwriting (all one word and capital letter) can be improved.

4) work on the formation of the letters.
Work on the formation of the letters. (Capital W)

5) Don't cut the line ( queue).
In BrE: Don't queue jump. Don't jump the queue.
In AmE (I think): Don't cut in line.

See above.