DNG, XMP, and Exporting

Question

The following pertains to Lightroom 1.1 (and possibly only to the Mac version on an Intel Mac with OS 10.4.10).
I have searched Lightroom 1.1 Help, the knowledge-base, this forum, and elsewhere for simple instruction on how to do either of the following:
Task #1: Create a separate XMP sidecar file from a DNG file for which the metadata relating to picture adjustments made in the Develop module has been embedded in the DNG file or stored in the Lightroom database.
Task#2: Export a DNG file (for which the development metadata has been embedded in the DNG file or stored in the Lightroom database) while at the same time creating a separate XMP file that contains the development metadata.
I did some experimenting relating to Task #2:
In Lightroom, I set the exposure of a DNG file to +4.00 in the Develop module, then switched to the Library module and clicked on the menu item "Metadata > Update DNG Preview & Metadata", and then exported with "Original" selected as the file format. Immediately after this, I set the exposure to -4.00, without updating, and then exported with "Original" selected as the file format. Immediately after this, I exported with "DNG" selected as the file format.
Here's what I found:
1. Looking at the thumbnail preview for each in Mac OS 10.4.10's Finder window: Exports 1 & 2 look like the picture did the last time I clicked on "Metadata > Update DNG Preview & Metadata" (i.e. with +4.00 exposure). Export 3 looks like the picture did at the time of the second and third exports (i.e. with -4.00 exposure). Opening any of these files within Mac OS X's Preview application shows the original state of the file without ANY of the development adjustments made before exporting.
2. Looking at the pictures in Adobe Camera Raw 3.7 (because I have only Photoshop CS2): Export 1 looks like the picture did the last time I clicked on "Metadata > Update DNG Preview & Metadata" (i.e. with +4.00 exposure). Exports 2 & 3 look like the picture did at the time of the second and third exports (i.e. with -4.00 exposure). No subsequent changes occur by going on to open the files within Photoshop CS2 after they are displayed in ACR 3.7.
3. Looking at the pictures after re-importing into Lightroom: Export 1 looks like the picture did the last time I clicked on "Metadata > Update DNG Preview & Metadata" (i.e. with +4.00 exposure). Export 3 looks like the picture did at the time of the second and third exports (i.e. with -4.00 exposure). For a few seconds, export 2 looks like the picture did the last time I clicked on "Metadata > Update DNG Preview & Metadata" (i.e. with +4.00 exposure). Then it switches to look like the picture did at the time of the second and third exports (i.e. with -4.00 exposure). It seems this has something to do with thumbnail previews being already embedded in the files and with Lightroom displaying them temporarily before updating them.
4. All three exports, when re-imported into Lightroom, begin with two snapshots already in the Snapshots panel of the Develop module: "Import" & "Import 2". "Import" is the original file condition when the file was first imported into Lightroom (before any of my export experiments). "Import 2" is the state of the file at the time I exported it, not the state when I clicked on "Metadata > Update DNG Preview & Metadata" (i.e. "Import 2" is with -4.00 exposure) EVEN IF THE CATALOG IS DELETED AND A NEW ONE CREATED BEFORE IMPORTING THESE, THE SAME THING OCCURS.
In none of these scenarios was an XMP file created. This had me wondering whether XMP files were possible at all in conjunction with DNG files. On to...
Task #1:
Now, as I was beginning to think that the only solution for creating XMP files from DNG files was to have Lightroom set up to maintain metadata in XMP files instead of in its own database (i.e. full-time XMP files as opposed to XMP files created only when exporting), I tried to alter settings in Lightroom's preferences, clicking menu

Answer 1

(to Lee Jay: Yes, as I found out.) Here's the rest of my post:
...items and buttons in this sequence: Preferences > General > Go to Catalog Settings > Metadata. Nothing I tried with the settings there would induce Lightroom to create XMP files alongside DNGs.
AFTER MORE WORK WITH JPGs AND CANON RAW FILES (.CR2), I FOUND THAT I COULD CREATE XMP FILES FOR THE CANON RAW FILES ONLY.
My conclusions are:
1. Lightroom writes separate XMP sidecar files for 3rd-party proprietary RAW formats only. This view is supported by the verbiage under these headings in Lightroom Help: "About metadata and XMP" and "Synchronize metadata with Adobe Camera Raw and Bridge".
2. This means that, for other formats, enabling the following catalog settings under Preferences does not result in separate XMP files: "Write develop settings to XMP for JPG, TIFF, and PSD", "Automatically write changes into XMP".
3. Also, for the other formats, enabling these catalog settings either does not alter the files at all or else alters them in a way that shows up only within Lightroom, Photoshop CS3, and any other applications that use Adobe Camera 4.0 or later. My additional export/re-import experimentation with JPGs in Lightroom suggests the latter is the case.
4. In Lightroom settings and documentation, "to XMP", "into XMP", etc. mean "to the XMP data embedded within the file", "into the XMP data embedded within the file", etc., except for those cases in which the associated file format is 3rd-party proprietary RAW, where these phrases mean "to a/the separate XMP sidecar file", "into a/the separate XMP sidecar file", etc.
5. The problem that seems to remain is that, apparently, not all non-Adobe software that can read DNG files is able to view changes made to these files by Lightroom (e.g. Mac OS X Preview).