Downloaded my iOS update 14

An iPhone 6 cannot support iOS 13 or later.

Maximum iOS list for iPhones below.

iPhone 2G - iPhone OS 3

iPhone 3G - iOS 4

iPhone 3GS - iOS 6

iPhone 4 - iOS 7

iPhone 4s - iOS 9

iPhone 5 and 5c - iOS 10

iPhone 5s, 6 and 6+ -iOS 12

iPhone 6S , SE 1, 7,7+,6S + - iOS 15

iPhone 8, 8+ and X - iOS 16

iPhone XS, XR, XS Max - iOS 17 (Beta)

iPhone 11 or later -???????

Just a wall socket adapter. No need to adjust the voltage.

Regards

Giulio

EDIT: Sorry, this answer had to be addressed to a different Author. Please ignore it.