The answers to your questions are too long and detailed for this user-to-user tech support forum. You really should take a full class in PDF accessibility (often called PDF Remediation) to better understand accessibility.
The TURO tool is where it has been since it was incorporated into Acrobat 20 (?) years ago. To access it:
- Select the Order Panel icon (left side of the screen). Looks like a blue "Z".
- From its options drop-down menu at the top (the square next to the circle-i), select Show Reading Order Panel (formerly called the TURO / Touch Up Reading Order panel).
- When this panel is visible on your screen, it is then active and you can select objects with its crosshairs and tag them.
Keep in mind that when using TURO, it will change the tags in the Tags Panel, including their Tag Reading Order, so you really need to have a solid handle on what you're doing to the PDF.
Sounds like much has changed with accessible PDFs since you last did this. Not only is the Acrobat interface different, but it contains more tools for accessibility. The PDF/UA-1 standard has been "refined," as well as the tools to achieve it.
No new tags are added to the document. And attempting to tag something as background/artifact does not remove it from the reading order,
By @spidersilk
It takes a bit more effort to artifact something with today's Acrobat. This changed (or broke, depending upon your point of view!) a couple of versions ago.
- From the Tags panel (not the Order panel), expand the element's tag so that you can see its internal yellow banker's box (the Content Container). You must first artifact the content, then the tag that wraps around the content.
- Right-click on the Content Container and select Artifact.

- In the next pop-up, select PAGE and ignore the "attach to sides:"

- When done, you'll see an empty tag in the tag tree — that is, it doesn't have an expansion arrow to its left nor a yellow Content Container nested inside. Just delete the now-empty tag.
And get a class in PDF Remediation! Mine are good <grin>. But some of the video courses are good, too.