Does the VoiceLive 3 have anti feedback ?
No. Probably not in the form you see in Correct.XT or Play Acoustic. Essentially, the "Post EQ" section of VL3 is perfectly capable of creating the same notch filter as Correct.XT or Play Acoustic, it's just done via some more complex looking settings. Phase invert is already available in the setup menu under the Guitar Tab. If you get feedback, the phase invert is a good first step to help.
The feedback can take different forms depending on which frequency the feedback is situated, the correction must be did on this particular frequency. Sometimes it is focused on a medium frequency, sometimes on bass frequency, sometimes on the high end and you get a terrible hiss. Set the level of the frequency at its minimum, - 18dB and turn the frequency post to "find" the feedback frequency.