I suffer from absentmindedness and constant worries during prayer, what should I do?
                                You should take refuge in Allah from the whispers of the devil and life worries. You should also seek Allah`s help and offer a lot of Istigfar (seeking the forgiveness of Allah). And Allah Knows Best.
                             
                        
                            
                                
                                My engagement to a young man was announced and blessed by both our families reciting Al-Fatihah. Is it permissible that I take off my Hijab in his presence?
                                All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon Prophet Mohammad and upon all his family and companions.
Reciting Al-Fatehah (The opening chapter of the holy Qura'n) to declare an engagement isn`t tantamount to a marriage contract and it isn`t permissible for him to see you without hijab or stay in private with you before the conclusion of the marriage contract. And Allah The Almighty Knows Best.
                             
                        
                            
                                
                                A sixteen-year-old young woman suffers from Alopecia, and lost her hair and eyebrows as a result. Is it allowed to draw her eyebrows using henna and an eyeliner? 
                                All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
It is permissible for women to use henna and what the asker has mentioned isn`t considered hair extension. However, if this young woman is proposed to, she must disclose this matter to the person proposing to her to avoid deception. And Allah The Almighty Knows Best. 
                             
                        
                            
                                
                                What is the ruling on not fulfilling a vow?
                                A vow is a commitment towards Allah, The Almighty, and so, it should be observed as much as possible, and it is impermissible to take it lightly. Allah, The Exalted, Says –in commending the believers (What means): "(Because) they perform the vow and fear a day whereof the evil is wide-spreading." [Al-Insan/7].