I like James' answers above, although all other attorneys are correct, because this requires an indepth discussion. At the risk of repeating...

Change in status

Hi: You cannnot start school until the F1 has been approved. I will file the I-539 six months before the intended start date of the school. ...

I140 not approved and visa expiring

The Labor Cert (LC) and I-140 are two separate processes. If you have not filed the LC, you will have to change to another status or leave the US...