This post has very good answers to the following questions :
Q. I am 61 but want to work until age 70. What happens to my wife if I die before I start retirement benefits?
A. The wife will receive survivor benefits equal to your retirement benefit, less any benefit she may be receiving.
Q. Why wasn't I offered retroactive benefits?
A. Retroactive benefits can't be paid prior to age 66.
Q. I am raising a grandchild who has a father in prison and an irresponsible mother. Can the child get benefits on my record?
A. Unlikely. Children can only get benefits if both parents are deceased or disabled.
Q. Can I get disability benefits at age 72?
A. No. You can get equivalent "retirement" benefits, but there are no "disability" payments after age 66.