What is the ruling on wearing a platinum ring with brilliant as its gemstone?

In women’s gatherings women give speech or recite nawha but thier voice is heard either directly or through a loudspeaker by passing men on the street. Is this permissible?

What is the ruling on relationship between a boy and a girl in cyber space without the intention of establishing a friendship?

What is the ruling on chatting on the Internet?

What is the ruling on giving a speech or presentation in university classes where non-mahram students are present and one has to stand before them? This would result in them looking at her, though she does not intend to draw lustful intentions. Take it into account that most students know each other.

Two years ago my sister started a relationship with a married man. Under the pretext of saving her from depression, the man told her to consider him as her brother and trust him. My sister trusted him and told him all her problems. The man, claiming that we are like brother and sister, established a relationship with her and even kissed her. Now my sister is so much dependent on him that her life has gone out of order. On the other hand, she considers herself a sinful person. She wants to know if God forgives her after all this and what she needs to do to be forgiven. What should be done with that man?