What is the ruling on swallowing saliva while fasting?
It is permissible for a fasting person to swallow their saliva because avoiding it would cause undue hardship and excessive strictness in religion. Islam discourages such excessiveness since Allah the Almighty intends ease for His followers and does not intend to put them in hardship.
What is the ruling on performing the Istikhara prayer after the Witr paryer?
Praise be to Allah, and peace and blessings be upon our Master, the Messenger of Allah.
The Istikhara prayer (Prayer for seeking guidance) is a Sunnah. It consists of two units (rak’ahs) performed outside of the obligatory prayers, after which the person supplicates with the traditionally narrated du’a. It is permissible to perform it before or after the Witr prayer, as the Istikhara prayer is recommended at all times except during the disliked times—the periods in which prayer is prohibited. This is because its specific reason (the Istikhara and supplication) occurs after the prayer itself, and any prayer with a subsequent reason is not permitted during the prohibited times. It should be noted that the two rak’ahs of Istikhara are not fulfilled by performing only one rak’ah, nor by a prostration of recitation (Sajdat al-Tilawah), nor by a funeral prayer (Janazah). And Allah the Exalted knows best.
Is it permissible for a young man and a young woman to enter into a covenant as a married couple without having a true seclusion (Khalwah) until their marriage contract is officially concluded?
The relation which isn`t based on a marriage contract is forbidden, and entering into a covenant as a married couple is unaccounted for and is from the evil suggestions of the devil.
Is it permissible for a praying person to make supplication in each Sajdah (a prostration) of obligatory prayer?
It is permissible for a praying person, whether praying individually, or in congregation, to make supplication during Sujood (prostration) in obligatory, or voluntary prayers. However, it is disliked for the Imam to do so since he is required to spare the prayer performers any sort of hardship, unless he is leading a certain group who don`t mind him extending the prayer.