How to stop IPhone 4 software update?

My mother brought an IPhone for me and I was informed that it's jailbroken. I have yet to figure out if it's tethered or unthethered, because I'm new to the term. I can't connect to Wi-Fi because there's a software update in progress that will continue when it's connected. How do I stop this?

1. Exit out of the program that is currently downloading a file or update. Press the single "Home" button on the bottom front of the phone. This will pause any update or download for that application.
2. Click on the "Settings" icon on the Home Screen. Scroll down to "Airplane Mode" and click the small toggle icon next to this option.
3. Tap on the toggle switch icon until it reads "Airplane Mode On." Airplane Mode immediately stops any cellular or Internet data transmissions--both ingoing and outgoing. The download will be stopped.
4. Hold down the "Sleep/Wake" button on the top right of the iPhone's casing. A virtual slider bar appears on screen. Use your finger to slide the slider bar arrow from the left side to the right side, which shuts the phone down.