tense - Difference between "is added" and "was added"

I need to know the meaning and tense of these sentences:

(A) "This feature is added to the last version."

(B) "This feature was added to the last version."

I can't understand the difference between "is added" and "was added". Is there any difference between these two sentences, or do they mean the same thing?

Answer

This feature is added to the last version.

is not grammatical. It is not now being added, since the last version is already out there.

This feature is added to the current version.

This feature is added to this release.

These sentences still do sound a bit off though, you would normally find them as:

This feature has been added to the current version.
This feature has been / is being added to this release.

("is being" if the current release is still in development.)

For others than the current version:

This feature was added in the last version.

This feature will be added in the next version.

"Is added" is used to describe a change in functionality based on some action or event:

This feature is added when you upgrade to the newest version.
This feature is added by selecting the option in the "options" screen.