* Did the Church ban Medjugorje in the 80s?
I think you are referring to the local bishop of the time. However, once the then Yugoslavian Council of Catholic Bishops found out, it was escalated to Rome. John Paul II then intervened and stopped the local bishop from interfering. He instead commissioned another investigation.
* Should I have reservation going there?
No. But don’t go there seeking miraculous spectaculars. Go there as a retreat. People typically go there and stay for at least a full week. I once stayed there almost 3 weeks. The high points there are not the apparitions, miracles of the sun, or visiting the visionaries. The real high point there is the daily evening prayer program, the Confession, the Mass, the Rosary and Way of the Cross walks, the Adoration chapel, and for me, getting to know the conversion stories of the locals and the visitors. Medjugorje shall be known as a conversion powerhouse, but it can only be so for you if you enter into its spiritual program.
* Should I venerate Our Lady of Medjugorje?
Mary allegedly called herself Queen of Peace at Medjugorje, Kraljica Mira. But this is not a new title of Mary. She has called Queen of Peace long before there was Medjugorje. And it is the same Mary! So, of course you can venerate Our Lady as Queen of Peace. Just don’t venerate Medjugorje.
And with that, you are also safe to practise her messages at Medjugorje, because they are not new either. Prayer, conversion, daily Mass, regular confession, reading of the bible… you cannot go wrong with them.
* What about the celebrity image of some of the visionaries?
Although I don’t know all six visionaries, this to me is very odd. It almost sounds like someone tries to find something to accuse the visionaries, and finding none, turn to attack their lifestyle as suspicious. Let’s focus on the fruits. If anyone of the visionaries is doing something that is contrary to the gospel, let’s testify to the wrong. If they seem to have money or a following, these things could very well be legitimate or even necessary for their work as well as raising their families.
As far as I know, three of the visionaries are very hidden, one is always sick, and the last two have done more than most to take the message of Medjugorje all over the world. They seem to me to be living the messages of Mary. I suppose they are not perfect, but let us not take scandal so easily. Again, let us focus on the fruits of their life, and the fruits of the messages of Medjugorje.