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.
Is it permissible for a woman in her menstrual period to recite from the Mus-haf (copy of the Quran ), or to recite by heart?
A menstruating woman is permitted neither to recite nor to touch the Quran according to what Ali Bin Abi Talib (May Allah be pleased with him) reported about the Prophet (PBUH) who was only held from reciting the Holy Quran by Janabah (Major impurity) [Al-Tirmizi in a sound Hadith]. Although Janabah and menstruation are major impurities, a menstruating woman is permitted to supplicate Allah (Duaa`) and make Zikr (Tasbihat ), even if these involved saying words from the Holy Quran, provided that she does not mean the words for themselves but as a supplication, or Zikr. Moreover, she is rewarded for not reciting the Quran during her menstrual period because she abided by the injunctions of Allah.
Is it permissible for a sick person to pray while sitting on a chair?
All perfect praise be to Allah, The Lord of the Worlds It is permissible for a sick person, who is unable to stand up, to offer prayer while sitting on a chair. If he/she was unable to prostrate while on the chair, the he/she should pray while sitting on the ground, but if he/she was neither able to bow (Roku),nor to prostrate, then he can do them while sitting on the chair. And Allah Knows Best.
Is a person who is in a state of Janabah (major ritual impurity due to having a marital intercourse, ejaculation, menstruation, and post-delivery impurities) sinful if he/she goes about his/her daily life activities in that state i.e. without making Ghusl (ritual bath)?
It goes without saying that a Muslim should always be in a state of ritual purity so as to be able to perform prayers and recite Quran. It is from Sunnah (Prophetic tradition) that a Muslim hastens to make Ghusl from Janabah, but he/she is not sinful in case he/she delayed that provided that he/she doesn`t miss prayers. However, it is permissible for him/her to go about their daily activities while in a state of Janabah, but had better bathe in order not to miss any prayer.