Welcome to HCM,
Thanks for trusting Healthcaremagic and submitting your query.
Answers to your queries is as following:-
(i) Sperms can survive only for a few days inside uterus
(ii) Ovulation generally occurs around 14th day of period. If you have sex around day of ovulation, a healthy sperm
can reach to an egg and fertilize it.
(iii) If your fetus is 12 weeks and 4 days old, you have probably conceived around 24th March,12.
(iv) Yes, it means you have not conceived during year 2011.
Hope you found my response to your query informative and helpful.
If you have further concerns in this regard, you can submit those with Healthcaremagic as well.
With good wishes,