Partially. Skype chat history is no longer available locally in main.db files,
but Skyperious can still be used to download new messages from Skype online service,
for keeping an archive of all chat history.
But any changes done to the database no longer affect what is visible in the official Skype program.
If login fails with
"Authentication Failure", it may be because of having
an original pre-Microsoft Skype account.
A possible work-around is to make an e-mail the primary alias of your Skype/Microsoft account:
Also, Skype login can sometimes fail for no discernible reason, giving errors like
"Couldn't retrieve field from login response" or
"That Microsoft account doesn't exist.". These failures tend
to be intermittent: try again after a while.
Yes, Skyperious has a command-line interface (help.html#commandline), which can be used to set up a periodic sync task to download new messages from Skype online service, e.g. using Task Scheduler on Windows or cron on Linux.
Yes, the main.db files were the same on all platforms: Windows, OS X, Linux, Android and iOS.
Yes, in source code form. See the installation guide.
No, it only worked with Skype.
If the file is an SQLite database, for example a WhatsApp message store, Skyperious will still open it. You can't browse chats or export messages, but you can access, search, and export database tables.
CSV by specification does not support non-ASCII letters, so they get converted to question marks. Export to an Excel spreadsheet will keep all characters.
SQLite usually wipes the deleted data clean instead of rebuilding the file
on each change. If you still want the file size to go down immediately,
VACUUM in SQL window.