Is it permissible to offer one Rak`ah in Witr prayer?
The minimum of Witr (An odd number prayer performed between Isha`a and Fajr) prayer is one Rak`ah, and the maximum is eleven, but the minimum of its complete form is three, and it is permissible to offer one only.
Is it permissible to make up for missed fast after the beginning of the second half of the month of Sha`ban (the month before Ramadan)?
Yes, it is permissible, but one who had missed fasts should hasten to make up for them. As for the Hadith mentioned in this regard, the prohibition is for offering absolute voluntary fasting. And Allah Knows Best.
Is it permissible to go to the bathroom wearing a necklace that has the word "Allah" inscribed on it?
All Perfect Praie be to Allah, The Lord of The Worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions.
Anything that contains words pertaining to Allah, The Almighty, is desired to be left outside when going to the bathroom, or to be hidden for fear of losing it. And Allah Knows Best.
Talking to one's fiancée in Ramadan with romantic talk may lead to arousal, and if pre-ejaculate fluid (Madhy) is discharged as a result, it does not break the fast. However, it is advised to avoid actions that provoke desire and lead to this outcome. If semen (Mani) is discharged as a result, it does break the fast.
The discharge of Madhy doesn't invalidate one's fasting but it invalidates the ablution and his clothes must be washed because they are impure in this case. As for Mani, it breaks one's fast and making up invalidataed is obligatory, beside; a Muslim suitor should abstain from these matters during Ramadan and not to degrade the holy month to this extent. And Allah Knows Best.