Thank you very much for your great clarification in Reply #12. Much appreciated.
Thank you very much for your interest to this issue. Actually, I am a native of Ukraine. Unfortunately, conversions of Catholics to Orthodoxy are not very common in Ukraine (said with all the respect to Catholics). Fortunately, here in UOC-USA we are blessed to have excellent clergy and laity, who were Roman Catholics or Eastern Catholics in the past.
I do believe that variant #2 is applied. And I will double check with experts. Right now, it is a little too late to call, sorry. Variant #1 (re-Baptism) is definitely excluded. Variant #4 is also not the case, while theoretically it could occur as a mistake of some priests. For sure, the same rules apply for both Roman Catholics and Eastern Catholics.
Ordinations of both Roman Catholic and Eastern Catholic clergy in case of their conversion to Orthodoxy are considered valid; therefore no re-ordination is required. Again, in Ukraine I can recall only one such case - Fr. Mykola Makar, an Eastern Rite Catholic, ordained in USA, converted in Ukraine, hold a position of the Prorector (Vice-President) of Kyiv Theological Academy and Seminary, now serves in France at the diocese of Moscow Patriarchate. As it has been mentioned, in USA and Canada, UOC has some great ex-Catholic clergy of different nationalities, some of those converted in lay status and ordained in the Orthodox Church.