What is the recommended supplication (Du'a) upon breaking the fast, and is it recited before or after breaking it?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah.
It is recommended (Mustahabb) for a fasting person to recite upon breaking the fast—that is, immediately after eating or drinking—the supplication: "Allahumma laka sumtu wa 'ala rizqika aftartu" (O Allah, for You I have fasted, and with Your provision I have broken my fast).
This is because our master, the Prophet (peace and blessings be upon him), used to say this. The narration was recorded by Abu Dawud with a good (Hasan) chain of transmission, albeit in a Mursal form (a narration where a Successor reports directly from the Prophet). Shaykh al-Islam Imam Ibn Hajar al-Haytami (may Allah have mercy upon him) stated: "Its Mursal status is inconsequential, as it pertains to virtuous deeds (Fada'il); furthermore, it was connected (Mawsul) through another chain of transmission." [Tuhfat al-Muhtaj, Vol.3/P.425]
It is also recommended to recite: "Dhahaba al-dhama'u wa ibtallat al-'uruqu wa thabata al-ajru in sha' Allah" (The thirst has gone, the veins are moistened, and the reward is confirmed, if Allah wills).
This was recorded by Abu Dawud with a good (Hasan) chain. Our leading jurists (Imams) have explicitly stated that it is recommended for the fasting person to combine both supplications.
Imam al-Bajuri (may Allah have mercy upon him) stated:
"And his saying following his breaking of the fast—that is, it is recommended to say: 'O Allah, for You I have fasted, upon Your provision I have broken my fast, in You I have believed, to You I have submitted, and upon You I have relied. The thirst has gone, the veins are moistened, and the reward is confirmed, if Allah wills. O You of vast bounty, forgive me. Praise be to Allah Who aided me so that I fasted, and provided for me so that I broke my fast. O Allah, grant us success in fasting, enable us to stand in night prayer during it, and aid us in it while people sleep, and admit us to Paradise in peace.'" [Hashiyat al-Bajuri, Vol.1/P.562]
Furthermore, the fasting person may supplicate with whatever good he or she wishes, for the supplication of a fasting person is answered. Al-Bayhaqi recorded on the authority of Anas ibn Malik that the Messenger of Allah (peace and blessings be upon him) said: "Three supplications are not rejected: the supplication of a parent for his child, the supplication of a fasting person, and the supplication of a traveler." And Allah Almighty knows best.
What is the ruling on using snuff, inhaled vapor, or menthol rub (Vicks) during the day in Ramadan?
Using snuff, inhaled vapor, or menthol rub (Vicks) invalidates the fast because these substances enter the lungs through inhalation, and the lungs are considered part of the body cavity (jauf).
Whoever uses them must refrain from eating and drinking for the rest of the day out of respect for the sacred month and make up for that day after Ramadan.
However, if it is merely a scent and none of its substance reaches the body cavity, it does not break the fast.
When is it Sunnah to slaughter the 'aqīqah?
All praise is due to Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
It is Sunnah for the 'aqīqah to be slaughtered on the seventh day from the birth of the newborn. According to the sounder position, the day of birth itself is counted as the first of the seven days. Thus, for example, if the child is born on a Saturday, the 'aqīqah is to be slaughtered on the following Friday. If the child is born at night, the count begins from the day that follows. And Allah Almighty knows best.
Is it permissible for one to shake hands with his uncle`s daughter?
No, it isn`t because he is a non-Mahram (Marriageable) to her.