Advice on upgrade legacy app from 1.7.0?

There have been changes to both the ./application and ./system folders since version 1.7.0

So you cannot just copy some files over.

you need to copy the ./system folder on every new update but if changes were made to
the ./application folder then those files will also need to be copied over.

What did you Try? What did you Get? What did you Expect?

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