The canonization of saints is not as centralized of a process as it is in the RCC. When a particularly holy person dies, then at times, a local “cult” (for lack of a better term) will pop up. If it gains enough influence, then the saint might be investigated by the synod of the national/autocephalous church to see if there is any cause for canonization (miracles, etc.). Unlike the RCC we don’t really have a set number of confirmed miracles needed to canonize a saint. In many ways, it’s like the process in the RCC (the formation of a local “cult” which attracts the attention of the authorities), but in the EOC, there’s no central authority for canonization; if an autocephalous church canonizes a new saint, then the saint is generally regarded as b being legitimate universally. Also, martyrdom is always considered to be enough cause for canonization within the EOC.
With transubstantiation, you will find varied opinions (some, especially the highly anti-Roman will reject it, while others accept it or are neutral on the matter). There is no doctrinal definition of how the bread and wine become the true body and blood of Christ; we just hold that it is a mystery. I think the most major objection to transubstantiation might be that it works on the assumption that Aristotelian metaphysics ( the talk about accidents and substance) its the true framework for reality. That being said, it is a useful description for how Christ comes to be present in the Eucharist, but we just can’t know if the metaphysical assumptions it makes are true.
On original sin, I’m really not too sure how we differ, because I often get varied answers from Roman Catholics. Thee Orthodox tend to view original sin as having changed the very fabric of being, so to speak. By disobeying God, Adam and Eve brought death into the world. Death, inherited biologically, is just a natural consequence of living in this fallen world. We don’t really have a concept of there being a “stain” of original sin; hence there’s really no need for the immaculate conception, because it cleanses from the Virgin Mary a concept which we do not have, the stain of original sin.
… The Catechism’s entry on Original Sin and its consequences can be found here in case it helps your understanding of RCC teaching : scborromeo.org/ccc/p1s2c1p7.htm#III
