Apologetics

If Irenaeus and other early Fathers believed in the Millennium on earth and taught this doctrine, why is this not taught by the Orthodox Church (since its position is amillenialism).

Yes, it is true that some of the early Fathers were millenialists (St. Justin the Martyr, for example); Orthodox Christians are well aware of this and of the fact that St Justin acknowledges disagreements on this point of doctrine. However, we do not see these fathers...

What is the difference between Orthodox and Catholic understandings of apostolic succession?

There is indeed a different understanding, but it should be admitted that few are aware of it! For a good discussion, please see here: http://www.monachos.net/forum/showthread.php?8403-Successors-of-the-Apostles-or-successors-of-Peter Basically, in historic / patristic Orthodoxy, the bishop is Peter's successor, while the presbyters stand for the apostles and do everything a...