Completing the salaah individually if the imaam performs 3 rakaats

Q: Our imaam offered 3 rakahs instead of 4 rakahs in asr farz Salah and ended the salah. No one interrupted him for his mistake and all the people ended offering 3 rakahs, then people said it was only 3 rakahs completed so the imam repeated the 4 rakahs again and every body prayed 4 rakahs again.

My question is if a person is behind a imam in the above case and is aware that the imam has made a mistake can he individually continue the same Salah and complete it ?

Inheritance

Q: My grandfather died 22 years ago. He left behind a big house but the property was never distributed among the heirs. My grandfather has 5 sons and the eldest one (my uncle) used to live in that house with his wife and sons. Now my eldest uncle has died and my other uncles are planning to dispose off the property. I would like to know if the wife and sons of my deceased uncle inherit from this property.

Doing aqeeqah for one's family

Q:

1. I want to know that I have a son that is 11 months. I want to do my, my wifes and my sons aqiqah on the same day. Is it possible because I don't know if my aqiqah was done or not because in our family aqiqah is mostly done on the occasion of marriage.

2. Also, give me details about how I do and what to do on the occasion of aqiqah so that we are safe from unwanted thing.s

3. And also I want to know, does me and my wife have to give silver equal to the hair in charity or can I pay the same price in cash? 

Gaining knowledge of the development of the fetus through a scan

Q: As we recite the Holy Quraan and we see in Surat e Luqman that some kind of knowledge is with Allah and no one knows about that. For example when will it rain and what is inside of the women, either male or female and when and where will the person die. So nowadays we see the technology that every one knows that what is inside a female's abdomen. So is there controversial that the new tafseer will change from the old one and what answer will we give to non muslims when we explain these ayaats.