How I can get iOS 13 update

These are the iOS options based on iPhone Model --> You need to Identify your iPhone model - Apple Support

• iOS 15.2 —> 6S / 6S Plus, SE (1st Gen and 2nd Gen), 7 / 7 Plus, 8 / 8 Plus, X, XR, XS /XS Max, 11,11 Pro /11 Pro Max, iPhone 12, 12 Mini, 12 Pro, 12 Pro max, iPhone 13, 13 Mini, 13 Pro, 13 Pro Max
• iOS 12.5.5 —> Final release supported on iPhone 5S, iPhone 6/6 Plus, 

Learn how to--> Update your iPhone, iPad, or iPod touch - Apple Support

If you are experiencing any difficulty with third-party apps then please contact the app developer directly --> How to contact an app developer - Apple Support

Ask the App developer to release the app for lower iOS versions also. Netflix has done it.

An iPhone 6 isn't capable of 13 or above. Try downloading the applications to a newer unit on the same Apple ID first.

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