Is it permissible to single out Fridays, Saturdays, and Sundays to make up for missed fasting without fasting a day before ,or after each ?

Yes, it is permissible to make up for missed fasting during the aforesaid days, and it is also valid to offer non-obligatory and vowed fasting as well. However, fasting a day before or after each isn`t obligatory.

Is Zakah due on a woman`s saved gold?

Zakah(obligatory charity) is due on saved gold if it reached Nissab(minimum amount liable for Zakah), and a lunar year had lapsed over owning it. The due Zakah is (2.5%).

Am I permitted to perform more than one prayer within single ablution?

You are permitted to pray as many as you could within one ablution and to recite Quran so long as your ablution isn't nullified.

Is it allowed for me to donate a flat to each of my children except one considering that the tuition fees I paid for the latter`s university study are equal to the price of the flat? In other words, he has received his share and this is why I`m donating a flat to my other children?