Redmine

Hello, could anybody help me out of trouble please:
I'm running multiple projects and added custom fields to all
projects.
The database was imported from SF some time ago, but I'm not
sure if this relates to my problem:
First of all, when I add the custom field 'Target Version'
I now have, for existing products, two Target Version entries:

However, in the corresponding 'custom field' Administrator section,
there is only one entry.

The newly added 'Target Version' doesn't show the handy, green
'plus' symbol next to it, and I couldn't find the setting where
to enable it.
Furthermore, the newly added 'Target Version' also shows, when
I click on it, even closed (past) versions of the project, which
the other 'Target Version' doesn't (it only shows open project versions).
How can I resolve this issue, i.e. only one 'Target Version' field; show the
green 'plus' symbol, as well as display only open project versions?
***Resolved: 'Target Version' is a standard field! When creating a new
project, this field is disabled by default, you have to add a version once
under 'Settings' to have this field displayed.