maybe you can answer for that one i wonder 2 for that issue.
1) LR saves a new database backup each time the user requests one. Is it reasonable to delete all previous backups?
I keep a few backups, just in case something goes wrong. The last back might also be corrupted... so keeping a few ones makes sense - at least for me.
2) LR will not save identical database backups to multiple drives; correct?
This is correct. It's your job to make copies to different drives.
3) LR installs itself in the MyPictures folder (PC), however, if one directs the database backup to a different drive, no backup exists in the MyPictures LR folder; correct?
Correct - But I'm using a Mac and I guess that on a PC Lightroom adopts a similar behavior. As far as I remember, you can specify the path of your backup folder when the backup folder pops up.
4) Is there a difference between database backup in LR 1.0 and 1.1? My older backups have the LRDB file, the later ones an LRCAT file?
Yes, the LRDB is the old format associated with Lightroom version 1.0. LRCAT is the new format. Lightroom version 1.0 won't be able to open the new file format. Lightroom version v 1.1 will be able to convert the old format and then read the converted file.
5) The LR folder in MyPictures has a "Photos" subfolder. The subfolders in that folder do not correspond to my LR folders. What is supposed to be in the Photos subfolder?
I don't know. It all depends on the options checked (like arrange in sub-folders) during import.
6) Other than "Backups" and "Photos" the LR folder in MyPictures has two other subfolders: "Lightroom Catalog Previews" and "Lightroom Metadata". These two folders do not appear do be copied to the Backup folder. So, if my C drive crashes, is the backup folder that I've directed LR to create on an external drive sufficient to restore everything once I reinstall LR on a "fixed" C drive?
Previews are generated automatically if they are missing. The "Lightroom Metadata.lrdata" is empty on my Mac.
7) What is the best advice for saving everything required to fully restart LR? I have LR pointed to one external hard drive, a full copy of which is on a second. In addition I have dual DVD copies of all raw files.
Personally, I keep multiple copies of my RAW files and Lightrooms files on hard drives. Those hard drives are stored on and off-site. Safety is in redundance.