Official firmware download list, Singapore region –
Singapore – http://samsung-updates.com/details/11782/Galaxy_Ace_2/GT-I8160/XSP/I8160XXMF2.html
Singapore (starhub) – http://samsung-updates.com/details/11780/Galaxy_Ace_2/GT-I8160/STH/I8160XXMF2.html
Singapore (singtel)- http://samsung-updates.com/details/11777/Galaxy_Ace_2/GT-I8160/SIN/I8160XXMF2.html
For other regions, find out yours → http://samsung-updates.com/device/?id=GT-I8160
How to install ? → http://theinhtikeaung.com/2013/05/16/official-update-jellybean-4-1-2-for-galaxy-ace-2-i8160/