Returning multiple old devices for a new purchase at an Apple Store

Can I go to an apple store to return all my old devices ( more than 12 years)

Can you? Yes you can, but you should not expect any credit for items older than 5-6 years. Apple will simply recycle those items.

The items that do have some value can be used as trade ins against the purchase of a new phone.

The older the device, the less trade-in value it will have, even in good condition. At some cut-off point, the trade-in value will be zero, and then those devices can only be taken in for recycling.

See: Apple Trade In - Apple (US) for expected values per device.

E.g. iPhone 7 Plus (2016) or earlier will have no trade-in value.

In general, the trade in value will be less than what one might expect from the user-to-user second-hand market.