Where should a woman who is led by her husband in prayer stand?
All perfect praise be to Allah The Lord of The Worlds It is from Sunnah (Prophetic tradition) that she stands behind him. And Allah Knows Best.
Which is better during the day in Ramadan: reciting the Quran or performing voluntary prayers?
A Muslim should establish a daily schedule for reciting the Quran in Ramadan.
Once they have completed their daily portion (known as a wird or hizb), they can engage in other acts of worship, including voluntary prayers (nawafil). Prayer itself is called "Quran", because a significant part of it involves reciting the Quran.
Allah says: "BE CONSTANT in [thy] prayer from the time when the sun has passed its zenith till the darkness of night, and [be ever mindful of its] recitation at dawn: for, behold, the recitation [of prayer] at dawn is indeed witnessed [by all that is holy]." [Al-Isra`/78]
Can a woman perform I‘tikaf in her home?
No, a woman's I‘tikaf is not valid if performed at home, because her home is not a mosque.
Is it permissible for a woman to give the ransom (Fidyah) for breaking her fast to her granddaughter (her son`s daughter)?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
It is permissible for a woman to give the ransom (Fidya) for breaking her fast in Ramadan to her granddaughter (her son’s daughter), provided that the girl is poor and her basic needs are not being met by the maintenance (Nafaqah) of those who are lislamically obligated to provide for her. And Allah the Exalted knows best.