it wasn't my intention to be vague at all, I simply felt that I responded to your question already.
Anyway to be very specific, If I have comitted a severe sin (a grave sin according to the RCC catechism, with culpability and with full consent of the will) I'm required to seek confession before recieving communion.
I'm allowed to confess at all churches in communion with Rome.
This includes all of the Eastern churches aswell, such as the Melkits, Ukrainian Catholic, Greek Catholic etc aswell as of course the Latin Church.
I'm also allowed to recieve all of the sacraments in the Orthodox Church if I'm far from my nearest Catholic Church and/ or in case of emergency (such as deathbed etc).
This does not mean that the Orthodox Church feel likewise just to clarify that.
a Orthodox Priest are free to refuse this arrangement if he like, but IRL it's very rare that they refuse this in a case of emergency.
I hope this is detailed enough