Activation Error iPhone 6s Preserved with iOS 9.3.5

I have an iPhone 6s with an update that still has the format and features of iOS 9.3.5. And as long as it was offline, I was capable of using it, usually to view pictures and see social media messages that would be restarted if I somehow were to turn on the WiFi. So I never did the updates nor the WiFi. In 2018, I turned on my iPhone to view the pictures that were never saved iCloud and then until the battery died.

However last year, in 2023, I once again decided to charge and turn on my iPhone 6s just to revisit the style update of 9.3.5 as I have been preserving it all those years and was successful of accessing the apps. But when I turned it off and then a few minutes back on, it would not let me get to the Home Screen. Instead, I was told to choose a WiFi connection. I could not access anything other than the option to access iTunes if I were to go without WiFi. However iTunes no longer exists on the present Mac so there is no app anymore. I tried every other option. From turning my phone off and back on, restarting it, and eventually turning on the WiFi of my phone, all I keep getting is the Activation error. Today, I connected my phone to my Mac. Nothing works. I kept getting the same message as my iPhone:

"Activation could not be completed. Please restore the iPhone and install the latest version of iOS and attempt activation again."

Some of the Apple employees at the store even convince me to make an appointment and they'll have my phone reset, but it will clear out everything I have. I mean, the problems persist after all attempts but I don't want to lose everything. I don't know what to do. Even though my phone convinces me to update, I can't since I am stuck at the Activation screen and Lock Screen has a greeting with no other button for me to press and there is no way I can bypass it.

I feel that if I never turned off my phone in the first place, rather let the battery die on its own like I did back in 2018 then I would still be using my phone offline! The only question I can ask other than what can I do for this issue to be resolve is using a computer that still has the iTunes app. Newer Mac computers only have Apple Music and iTunes is only a store now. Please I need answers.