No, the Masters is the same length. The benefits of "Promotionsorientiertes Masterstudium" only pay off after the Master’s degree, in that it allows you to contribute to your PhD while still taking classes.

Familiarize yourself with the work of the group by reading the groups web pages, looking up members of the group on google scholar, and talking directly to members of the group.

Absolutely. Typically, you would apply informally towards the end of your Masters degree. Just talk directly to the groups you are interested in.

The default case is that you will be in the program until you achieve your PhD. That said, membership in the program is granted on a year-by-year basis and expects that you continue to produce excellent results as judged by your advisor.