While I'm unsure about the second question, the first question relates not to talaq, but to khula. Google "khula" at the fatwa site of your choice to find out the specifics. At the very basis, the evidence for khula comes from the Prophet (saws):

Narrated Ibn 'Abbas (ra): The wife of Thabit bin Qais came to the Prophet and said, "O Allah's Apostle! I do not blame Thabit for defects in his character or his religion, but I, being a Muslim, dislike to behave in un-Islamic manner (if I remain with him)." On that Allah's Apostle said (to her), "Will you give back the garden which your husband has given you (as Mahr)?" She said, "Yes." Then the Prophet said to Thabit, "O Thabit! Accept your garden, and divorce her once." (Sahih Al-Bukhari)


From this, we return the mahr.