Summarized Fatawaa
• Is it permissible for a woman to swear a false oath by the Holy Quran to please her distrustful husband?
It is forbidden for a person to do so since this is considered a false oath(Yamaan Ghamoos) which dips(Yaghmos) its taker in Hellfire if he/she doesn`t seek repentance, and he/she has to expiate for that oath. You should avoid any doubtful acts so that your husband`s chest remains clear from the evil suggestions of the devil.
• Is it permissible to undergo plastic surgery only for adornment?
Plastic surgery is an exaggerated adornment, and a surrender to the will of the devil. However, in urgent cases such as having an extra toe that causes harm, such procedure is permissible, and applies to men as well.
• Does Istigfar(saying astagfiru Allah) between the first and the second part of Friday prayer`s sermon render the prayer invalid?
Talking during Friday prayer`s sermon is disliked, but there is no harm in offering Istigfar between the two parts of the sermon, and it doesn`t invalidate the prayer as it is actually from Sunnah.
• Is `Iddah(waiting period) incumbent on an old lady whose husband had died?
Upon the death of the husband, `Iddah is incumbent on the wife regardless of her age.