Is it incumbent on the fiancée to obey her fiancé?
When the woman settles in her husband`s house, it is incumbent on him to provide for her and it is incumbent on her to obey him. Before that, and if the marriage contract had been concluded, then she is lawfully his wife and thus she should abide by custom in treating him, but if the marriage contract hadn`t been concluded, then she should treat him as a non-Mahram (Marriageable).
Is the niṣāb calculated based on the price of 21-karat gold, or 24-karat gold?
All praise is due to Allah, and peace and blessings be upon our master, the Messenger of Allah ﷺ.
Zakāh is obligatory on cash and on gold designated for saving or for trade, provided the total reaches the niṣāb (minimum threshold liable for zakah), and a full ḥawl (lunar year) has elapsed over it. The niṣāb is (85) grams of 24-karat gold; for 21-karat gold, the niṣāb equals (97) grams; and for 18-karat gold, it equals (113) grams.
The relied-upon position is to calculate the zakāh based on the buying price [i.e., the price the gold merchant would pay the owner to purchase the gold from him] on the day the zakāh obligation is due.
The one paying zakāh may assess/calculate the niṣāb using any of the aforementioned gold karats [i.e., he may choose whichever karat standard he wishes for the purpose of the calculation]. And Allah, the Exalted, knows best.
Can I start fasting based on the moon sighting of another country?
You must follow the moon sighting of the country you are in.
What is the ruling of Islamic Law on participating in the prize draws (raffles) that commercial stores hold for their customers?
Praise be to Allah, and peace and blessings upon our master, the Messenger of Allah.
There is no objection to participating in the prize draws (raffles) that commercial stores hold for their customers, provided that the buyer's intention in purchasing is not merely to enter the competition without any need for what is bought — rather, the purchase must be genuinely intended for the item itself, and one must not pay more than the item's fair market price. This is because paying an amount above the market price would effectively be paying a fee to enter the prize draw, which would render it a form of gambling (qimār).
These prizes are, in essence, gifts that businesses offer through a random drawing (qur'ah) to those who purchase from them, as a means of encouraging sales, without the customer bearing any additional monetary cost for participation. So long as the aforementioned conditions are met, there is no objection to benefiting from the prize offered by the store, as it is considered a lawful prize from the viewpoint of Islamic Law.
It is stated in the resolutions of the "Jordanian Iftaa' Board" (Resolution No. 47), in the context of outlining the conditions for permissible prizes: "The price of the ticket [or item purchased] for the sake of the prize must not exceed its original price, so that there is no payment of money in exchange for participation in the draw." And Allah, the Most High, knows best.