How to unzip a zip document with preview content in iPhone 7?

You cannot pick and choose an iOS version. What you get is Settings > General > Software update > [All options are available here]

You need to correctly Identify your iPhone model - Apple Support

These are the iOS options based on an iPhone Model

• iOS 15.8.2 —> iOS 15 is compatible with these devices.
  • Chipset A9 - 6S (2GB RAM) / 6S Plus (2GB RAM) / SE (1st Gen) (2GB RAM)
  • Chipset A10 - 7 (2GB RAM) / 7 Plus (3GB RAM)

Know how to...

• Update Over-the-Air (OTA) —> Update your iPhone or iPad - Apple Support (IN)
• Update using iTunes/Finder —> Update your iPhone, iPad, or iPod touch - Apple Support (IN)

Unzipping files on iPhone and iPad is a breeze! Just tap any zipped file in the Files app to extract its contents. Encrypted files? No problem, just enter the password when prompted.

However, it's important to note that not all archive formats are supported by iOS.

Simply tapping on a normal Zipped file can unzip the content directly on iOS devices even if they are encrypted.

Up date my phone