How do I use Versions on the modebar?

After an error, can I use the Versions option to get back to a previous state?
if yes, how do I use it?

Also, how often is an older version stored, and does it automatically delete old entries after a certain time?

All changes are versioned in real Time. If you expand the versions tree you will see its arranged by date and within date by time. Expand the time you want to revert back to and click on the file under the time sub-branch that you want to revert. This will be displayed in the file viewer panel on the right. On the top right if the header bar is a revert icon. Click it and the file will be reverted back to that version and the app reloaded.

you can roll back and forward to any point in time.

Yes you can.
Please see attached screenshot demonstrating how to restore the lianjademo App from the version saved at 12:16:05 on 05-Feb-2013. The lianjademo.lianja file is the main App file.
App files are backed up when you open the App, close the App or click Save App (Page Builder). Scripts (.prg, .js, .php etc) in an App are backed up when you save changes. Backed up files are not deleted automatically. They can be found in the 'backups' sub-directory of the App, e.g. for the lianjademo App on default installation Windows: C:\Lianja\apps\lianjademo\backups.

Link to screenshot: http://www.lianja.com/doc/images/1/1...ons_080213.png

Thanks for the info. Very useful capability.

Do the version backups files accumulate indefinitely?
Should one manually delete old ones?
Can one just delete the folder in Windows Explorer?

Yes they just go on forever.

You can select a branch for a particular month and click the delete icon in the header bar.

Yes you can delete in windows explorer just do it when you don't have the app builder running (although it probably will adjust the contents of the tree for you automagically).

Nice thing about the versions workspace is that you can roll backwards and forwards in time.

If you use dropbox for your development folders you get the advantage of automatic backups into the cloud as well.