How do I access my older photographs from when I first got my iPhone?

That would depend on what arrangements you made. When you got each subsequent phone, did you have the data and photos copied from the old phone to the new phone, or did you keep your data and photos in iCloud, or did you just start over again anew? Unless you copied everything from the first phone to the second to the third and so on down the line, the older data and phots would be left behind.

If you have been relying on iCloud to keep the continuity of your data and photos, you need to stay on the same Apple ID (now called Apple ID). You can rename it but not switch to a new one without the danger of leaving content behind.