When is Istikharah (guidance prayer) Du`a offered, before Tasleem (saying asalamu alikum warahmatu allah wa barakatuh to end the prayer), or after it?
It is offered after Tasleem.
The supplication: "O Allah, we do not ask You to avert the decree, but we ask You for kindness in it." Is this Supplication Halal or Haram?
We are obliged to supplicate Allah, so when supplicating we comply with Allah's Ordainments, and making supplications that are reported in the authentic texts is better. And Allah Knows Best.
Is it permissible for a Muslim to slaughter an Aqeeqah on behalf of someone else, and offer it to him as a gift?
In principle, the guardian is the one who should offer the Aqeeqah (the sheep slaughtered on the seventh day from the child`s birth) because he is obliged to provide for the newborn, and it is impermissible for anyone else to slaughter it on his behalf unless with his consent. However, it is permissible for a person to offer the sheep, or its price as a gift to the guardian of the newborn, and then the latter can slaughter it, or deputies someone else to do that on his behalf.
I suffer from excessive gas, especially when I pray, and I redo my ablution more than seven times. I have obsessive thoughts about this matter, even though I went to a doctor and was given medication that did not help. What should I do?
If the release of gas stops at certain times between prayers, you should wait for that time, perform ablution, and pray. However, if it is continuous, you should perform ablution after the prayer time begins and pray, and the release of gas during the prayer is excused. And Allah The Almighty Knows Best.