Why was the exact date of Laylat al-Qadr concealed?
The wisdom behind this is to encourage Muslims to strive in worship throughout all the nights of Ramadan, or at least in the last ten nights. By doing so, they will earn the reward of observing Laylat al-Qadr as well as the reward of worshiping on other blessed nights.
Should a prayer performer who forgets to offer the middle Tashahod (saying ash-hadu anala ilaha ila-alah) offer Sujood As-Sahw (prostration of forgetfulness)?
He/she should offer two prostrations of forgetfulness at the end of the prayer. And Allah Knows Best.
Is it a condition that a woman should untie her locks while making Ghusl (ritual bath)?
Ghusl from Janabah (ritual impurity), or menstruation obligates that water reaches the roots of the hair in order for the Ghusl to be valid, but if it doesn`t, then hair locks must be untied for water to reach them, and for Ghusl to become valid.
What is the ruling on having an intention (Niyyah) for every prayer?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
Intention (Niyyah) is a pillar (Rukn) without which the prayer is not valid. The worshiper must have an intention for every prayer, meaning they must consciously intend the act of worship they are performing. Its timing must coincide with the opening Takbir (Takbirat al-Ihram). It is not a requirement to utter it verbally; rather, doing so is considered a recommended Sunnah. There are three levels of intention:
1-If the prayer is obligatory (Fard): It is mandatory to include the Intent (to pray), the Specification (which prayer, e.g., 'Asr), and the Obligation (recognizing it as a Fard). For example, one should bring to mind or say: 'I intend to pray the Fard of 'Asr.'
2-If it is a voluntary prayer restricted by a specific time or cause (Sunnah Muqayyadah): It is mandatory to include the Intent and the Specification. For example: 'I intend to pray the Sunnah before Zuhr' or 'I intend to pray Duha.'
3-If it is an absolute voluntary prayer (Nafl Mutlaq): It is sufficient to simply have the Intent to pray. For example: 'I intend to pray.'
And Allah the Exalted knows best.