oct2005

You do not have to enter the US before age 21. You can enter after turning 21 if you have your visa. Turing 21 before getting a visa is another issue.
The expiration date is on the immigrant visa. generally, an immigrant visa is good for six months after the medical exam .

Nobody can really tell when your case moves from one step to another. It depends on how fast are u in submitting needed documents to NVC. Once all documents are ok, you will receive a case completion notice. You will then need to wait for an interview schedule for u. As of now, someone with PD of FEB2012 got IL. The PD really moves fast and it could become current soon

You put your current age. Why would you put 21 when you're expecting to submit the form this month (July)?