Can I install iOS 13.4 my iPhone

No, the best that the iPhone 6 can do is iOS 12.5.7

If you want to run higher iOS versions, you will need a new phone.

shravani257 Said:

"Can I install iOS 13.4 my iPhone"

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For future Reference...

Updating an iPhone 6:

Update Using a Computer:

Have a Computer Handy? If so, try using a computer to update. Go here: Update your iPhone Using a Computer - User Tip. If any updates are availabe, they will install, sure enough.