my iPhone 6 has iOS 12.5.5 and will not up date, the up date list says 15.6.1 why

Your 8 year old phone cannot be updated beyond 12.5.5. Here is the device compatibility info:

• NOTE: iOS 16 is not available for any models except to iOS developers and beta participants. General release will be in Fall, 2022
• iPhone 12 or 13 series: You can update to 15.6
• Any model 6S or newer (including original SE, 2nd and 3rd editions): You can update to 15.6
• iPhone 5S or 6: You cannot update to iOS 13 or higher; you can update only to iOS 12.5.5
• iPhone 5: You can update only to 10.3.4
• iPhone 5C: You can update only to 10.3.3
• iPhone 4S: You can update only to 9.3.6
• iPhone 4: You can update only to 7.1.2

An iPhone 6 doesn't have enough RAM for 13 or above. If you're asking about the security patch, Apple will release an update to 12 if they decide one's needed.

(223180)

rkguc wrote:

can you add ram to iPhone 6

No.