Is jailbreak essential for install Cydia on iOS device? Yes, if you want to Cydia you have to jailbreak your iPhone, iPad or iPod Touch. That is the only way of successfully install Cydia on your device. Jailbreaking is the process of removing limitation of iOS on Apple devices. It allows to user greater control all over the device. Jailbreaking permits root access to the iOS file system. Jailbreak will open the door to unlock your iPhone. There are thousands of applications, theme and games to download for free through Cydia, just jailbreak your device. Reason for jailbreaking is to expand the features limited by Apple and its App Store such as device customization, use of handset on multiple carriers and early exploit fixes.
Is that jailbreak violating of low?? No really no, that is a right not only who uses iOS device but also other types of devices like that (Android- rooting). Jailbreaking is doing by specially designed tool, developed by the person/team. Apple iOS is engineered with strong security measures and jailbreaking is a significant technical challenge.
There are number of jailbreaking tools available in the world. EvasΟin, p0sixspwn, redsnΟw, GeeksnΟw, Pangu and newly release TaiG are the most popular as the jailbreaking tools which can jailbreak iOS and install Cydia to the iOS devices.
You can follow bellow link to refer jailbreak guide & install Cydia on you device..