How to determine the boundaries of a locality

Q: In beheshti zewar, in the chapter of salaah on a journey, mention is made that if the azaan from one place cannot be heard in another place, then they are regarded as two places, for the purpose of the musafir if he spends 10 days in each place, he would still be a musafir. Does this still apply today when determining where are boundaries? Or does one look at the municipal boundaries between suburbs and localities?

The Jews of Banu Quraiza

Q: I heard from critics of Islam that, in the seerah, when it comes to the Jewish tribe, Banoo Quraiza, the Prophet (Sallallahu Alayhi Wasallam) checked all the boys if they had pubic hair to determine whether they were mature and baaligh in order to be able to decide whether they should be treated and punished like all the men. Is there any truth to this? Also, were the Bnoo Quraiza judged for their crime by their own scriptures i.e. The Torah or were they appointed an arbitrator among the Sahaaba according to their (Banoo Quraiza's) choice?

Oral sex

Q: Is oral sex allowed with a covering? If a husband insists on his wife to perform such an act and she refuses, will she be disobeying her husband? What should she do?

Distributing zakaat

Q: In regards to discharging Zakaat, it has become very difficult now a days to find out who deserve to receive Zakaat. Please advise where else it can be discharged like muslim institutes, orphan centers etc?

Tahajjud Salaah

Q: It is mentioned in the Hadith that Voluntary Worship is a means of attaining proximity to Allah. Besides the Obligatory and Essential Prayers, the Holy Prophet (Sallallahu Alayhi Wasallam) used to make arrangements for the Voluntary (Nawafil) Prayers too.

1) I want to perform tahajjud namaz daily but when I sleep I don't wake up at the time of tahajjud. So can I just offer eight rakats Voluntary Worship for Allah before going to sleep daily?

2) Is it allowed to perform extra Voluntary Worship any time of a day and any time of night before going to sleep?

Hair transplant

Q: You had answered my question that hair transplant is not permissible in Islam which made me so confused because I am under the impression that hair transplant is using a person's own hair to transplant in the bold area, so how can this be not allowed? I understand that hair wig is not allowed but hair transplant is medical treatment to inject a person's "own hairs". Please clarify.