Can employers force employees to take vacation time during company shut down?

Yes.

Yes. Employers don't have to give employees a vacation, by law. So any policy they have about vacations can be legally enforced, unfortunately.

Yes, they can. But, here is a little known fact. If you have not been working with the company long enough to have a paid vacation and they have a two week break, you can sigh up for your unemployment, use the first week as your waiting week, and collect unemployment for the second.

Or, if you were receiving unemployment before you started with this employer and they have already applied your waiting week, you can reopen your claim and be paid for the first week.

Don't know if this helps in your case, if not, try to enjoy your vacation.

yes. it's a company vacation and that is when your vacation starts

Not sure where you live state laws may be in affect, but you can check here first.--http://www.nlrb.gov/nlrb/home/default.as...

Yes and no depending on state laws.
If you don't want to take your vacation then, sometimes you can take the close down on 'unpaid time off' and use your 'vacation' later.
Depends on state laws.
Now be glad you have a job or go look for an other on your time off.