What should a person who doubted having missed a pillar of prayer do?

All praise be to Allah, The Lord of The Worlds.                                                                                                                                                                              The prayer of one who doubts having missed one of its pillars is valid, and nothing is due on him/her since having a doubt after offering the act of worship doesn`t undermine its validity. And Allah Knows Best.

Who are the blood-relatives with whom kinship ties should be maintained?

Blood-relatives are those from the side of one`s father and mother: grandfathers, grandmothers, uncles, and aunts. And Allah Knows Best.

What is the ruling on a woman driving a car?

All Perfect Praise is to Allah, The Lord of The Worlds, and may His Peace and Blessinsg be upn our Prophet Muhammad and upon all of his family and compnions.

It is permissible for the woman to drive a car, but it is impermissible for her to travel unaccompanied by a Mahram (Unmarriageable kin). And Allah The Exalted Knows Best.

Is touching a non-Mahram woman invalidates person's ablution?

Touching non-Mahram woman is prohibited, and according to the Shafiee's, it invalidates the ablution. And Allah Knows Best.