Going back and forth between lightroom and photoshop

It's a bit unclear what you're trying to achieve here, but a word of caution: Roundtripping between Lightroom and Photoshop can very quickly become a self-defeating process. Mostly it's a recipe for endless confusion.

• Lightroom does not support or understand Photoshop layers. It just reads the flattened composite that Photoshop embeds in the file, and that's what it works with.
• Lightroom adjustments are stored in the catalog, not in the file. Photoshop does not read Lightroom adjustments, unless you specifically export with adjustments baked into the pixel data.

The standard workflow is to use Lightroom for processing raw files, taking that as far as you can, and then send a processed and rendered RGB file to Photoshop for further treatment that cannot be achieved with Lightroom. The process normally stops there.

If you want to use Lightroom adjustments on one of these rendered RGB files, you can reprocess it in Lightroom. But a much more efficient way to achieve exactly the same result is to use the ACR filter in Photoshop. It will give you not only the same result, but much more flexibility with layers, masking or treatment as a smart filter.

And to avoid further confusion: The ACR filter in Photoshop is not the same as the ACR raw processor plugin. It uses the same engine, but is intended to be used on RGB data and not raw data, and it behaves just like any other filter in Photoshop. And the effect is, again, the same as reopening the file in Lightroom.

Is that -

Lightroom-Desktop v4.2

Lightroom (Perpetual v1-v6)

Lightroom-iPad v6

Lightroom-Classic v10.2.2?

PC, Mac, iPad ?

Workflow re-opening the Photoshop 'original' file?