Summarized Fatawaa
• Is the father a Mahram(Non-marriageable) to his son`s mother-in-law?
The father is a non-Mahram(Marriageable) to his son`s mother-in-law, so it is impermissible for them to look at each other, or to have a seclusion(Khalwah).
• Is it permissible for a woman to have her underwear on while performing Umrah?
Yes, it is permissible for a woman to have her underwear on while performing Umrah. This is because she should keep her regular clothes that cover all her body while being in a state of Ihram(ritual consecration) for Hajj, or Umrah. However, she should uncover her face and hands, but it is permissible for her to let her head-covering garment drape from her head down over her face when non-Mahram (i.e., marriageable) men pass by her.
• How should I deal with the whispers of the devil with regard to ablution and purity ?
Whispers in ablution are from the devil, and so you should take refuge in Allah from the devil`s evil suggestions that aim to distort the religion. Thus, once an organ is completely pure, don`t question its purity since having whispers doesn`t mean that the purity is invalid as it has already been established.
• What should a praying person who doubts having offered one, or two prostrations in the third Rakah(unit of prayer) do?
Whoever has doubts about their prayer should consider what is less i.e. the above person should offer another Sajda(prostration) and complete his/her prayer, then offer Sujood As-Sahw(prostration of forgetfulness).