In the event that it is difficult to purchase a private Muslim cemetery or their request is rejected, and the current Muslim cemetery is full, is it permissible to reclaim the adjacent Christian cemetery and convert it into a Muslim cemetery? And are there specific conditions for that?

There is no objection to reaching an agreement with the church to reclaim a cemetery by removing deteriorated bones from it and dedicating it to Muslims. The Prophet, peace and blessings be upon him, reclaimed the land on which he built his mosque, and it contained graves of polytheists, so he exhumed them. It is permissible to exhume old, effaced graves if they are not respected, and to pray in the cemeteries of polytheists after their exhumation. If it is known that the deceased has turned into dust, or it is presumed so by the expertise of specialists, it is permissible to bury others in the grave, cultivate the land, and so on. If a dilapidated infidel cemetery is turned into a Muslim cemetery after moving its bones, it is permissible. However, wiping the surface of infidel graves and burying Muslims next to them while their bones remain inside is not permissible. It is forbidden to bury a Muslim in an infidel cemetery except out of necessity.