A person vowed to slaughter a sacrificial animal. Is he permitted to eat from it?
                                If the vowed sacrificial animal was for the sake of Allah, and the one who vowed didn't specify then its meat should be distributed only among the poor and needy similar to distributing Zakah of Al-Fiter so neither him nor his dependents permitted to eat from; however if his vow was to made a banquet and invititing his relatives and others; then he must bring up as much as he can from its meat for them. In addition, he is permitted to eat from it in a reasonable basis. And Allah Knows Best. 
                             
                        
                            
                                
                                Is Zakah (obligatory charity) due on leased property, and how is it calculated?
                                Zakah isn`t due on the leased property itself, but on the saved income from that property if it reached Nissab (minimum amount liable for Zakah), and a whole lunar year had lapsed over saving it.
                             
                        
                            
                                
                                Is the one who gives up on marriage because he can`t afford it considered sinful?
                                Marriage is desirable, but one who can`t afford it isn`t considered sinful. However, he should supplicate to Allah, and seek His forgiveness.
                             
                        
                            
                                
                                Should the father command his ten-year-old daughter to wear the Islamic dress?
                                All perfect praise be to Allah, The Lord of The Worlds, and may His Peace and Blessings be upon our Prophet Muhammad and upon all of his family and companions.
The father should order his daughter to put on the Islamic dress once she turns ten, in order for her to get used to it. And Allah Knows Best.