First, read the English article below.

In the context of the iPhone community, jailbreaking means removing the many restrictions Apple has implanted in iOS. For those who are very committed to having a customizable iPhone, this is perhaps one of the best options. However, it isn't for everyone.  Check if jailbreaking your iPhone will void its warranty. Unless you are very experienced with jailbreaking, you may want to wait to jailbreak your iPhone until the Apple warranty expires 1 year after purchase.   Apple has attempted to create an environment that--because it is highly regulated--is safe for virtually all users. You don't have to worry about malware or scams like you would without the protections provided by Apple restrictions. Make sure you have a backup of your files before you make any switch, just in case anything bad happens.   Update iTunes to its latest version. Back up your iPhone on iTunes and/or with use of a cloud. Select a jailbreak program. Programs like RedSn0w or RageBreak are options. You should research the newest and best programs for jailbreaking your iPhone model. There are a number of options out there, but determining which is best can be tricky unless you know people who have had success with one particular program. These are, after all, not Apple-approved programs and thus have not been professionally vetted. Many of these programs are updated to work on particular versions of iOS and not on later varieties (often because Apple intentionally alters the operating system to prevent jailbreaks). It is very common that, for example, a program can work on iOS 8.1.1 but not 8.1.2. There should be information available discussing what the program can and cannot do. You will actually have to download the file to a separate computer in order to complete the jailbreak process.   Download a jailbreak program onto your computer. Install the program onto your computer. Remember, it may provide you a passcode to use later. Do record it and keep it at hand. Download the latest iOS firmware. You can find the firmware file... 

Now, please write a short abstract for it in Vietnamese. Abstract:
Tìm hiểu về bẻ khóa (jailbreak) iPhone. Cập nhật chương trình và lưu tập tin. Cài đặt chương trình bẻ khóa. Đừng quên bước chuẩn bị để liên kết máy tính và iPhone. Hoàn thành quá trình bẻ khóa. Cài đặt Cydia (nếu thích hợp). Khởi động lại iPhone. Khởi động Cydia. Chọn biểu tượng của ứng dụng tùy biến trên màn hình.