Benifits

I have not seen the ability to turn retirement benefits on and off as you are seeking.

There is a way to essentially rescind your decision to take early benefits by filing a "Request for Withdrawal of Application" SSA-521 form :
http://www.ssa.gov/online/ssa-521.pdf

With this you can "undo" your decision to receive early benefits, but you'll have to repay all the benefits you received (but without interest).

Here are some details on this :
http://www.kiplinger.com/features/archives/2008/02/krr-tactics-for-takin...

Here are a couple other links that may be useful for this :
http://www.ssa.gov/pubs/10069.html
http://www.ssa.gov/retire2/retcalc.htm

You will need to apply for and qualify for SS retirement benefits. You can do this online, or visit a local Social Security office. You will need documentation such as birth certificate, last year's W-2 etc.

Your monthly benefit increases as you delay the receipt of benefits, so no, benefits do not start "the first day of retirement".

Direct deposit of monthly payments into your bank account is preferred to check mailings.

Here are some details :
http://www.ssa.gov/pubs/10035.html#know
http://www.ssa.gov/deposit/