Do I have a choice as to when I should apply for benefits?
Yes you have a choice. You should make an informed decision about when to apply for benefits based on your individual and family circumstances.
how many credits do they need to provide in order for their survivor to be eligible for Social Security Benefits?
The number of credits needed to provide benefits for survivors depends on the worker's age when they die. No one needs more than 40 credits 10 years of work to be eligible for any Social Security benefit