He's not a member of the Church (russian orthodox boy), but being justified, he would be joined to it by grace through implicit baptism of desire.
That he has had water baptism is irrelevant (or, are you saying the Orthodox are members of the Church in virtue of their water baptism?).
I don't wan't to get too deep into your example, but it was quite contradictory. If a person is baptized, they are members of the Church. If a russian orthodox boy dies in the state of grace, they go to heaven. Duh.
But your example presumed that the boy could have BOD post-baptism. You only have BOD once, just like you can only get baptized once. Unless you think one can receive BOD multiple times?? ??
The question of if a justified but unbaptized person goes to heaven is up to God. If that's what the Church says, I'll believe it, but I think it's debatable. You don't. Let's move on.
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The real question is: Who is able to receive BOD? Trent was VERY SPECIFIC about who qualifies to be justified by BOD. Your (and +ABL's) heretical theory that a muslim "who wants to do what God wills" can receive BOD is an error. Trent taught that said muslim must believe in 1) original sin, the Incarnation, Trinity, Christ's sacrifice on the Cross, 2) learn and accept the faith/Church, and 3) make a decision to follow the 10 commandments and "begin a new life" in the Church (i.e. through baptism - whether expressed openly (explicitly) or implied by actions (implicitly).
No ignorant person COULD EVER qualify the above requirements. Hence, they cannot receive BOD.
No non-catholic, still practiciing their false religion, COULD EVER qualify for the above requirements. Hence, they cannot receive BOD.
You're main problem is a lack of understanding of what "implicit" means. You falsely define implicit desire as meaning "subconscious" or "undefined/unspecific". As if a muslim can become a member of the Church, only knowing the catholic dogma on Adam/Eve. As if a muslim can join the Church through "good will" and a "desire for God" without knowing what baptism is or means (both errors condemned by Trent).
Implicit simply means 'implied but not expressed'; or "essentially connected with". So a person who is attending catechism classes - they are IMPLICITLY showing they want to become catholic. A catechumen who goes to sunday mass is "essentially or very closely connected with" the Faith. One who is ignorant of, or practicing a false religion, by definition, cannot love the Faith, and is not essentially or closely connected with the Faith. Therefore, BOD is not possible for them, per Trent.
The modernists have subtly replaced "implicit desire
for baptism/Faith" with "implicit desire
for God" and thus have turned BOD into heresy. They have corrupted EENS, in an effort to create their hoped-for freemasonic, satanic, one-world religion, which necessarily is opposed by the Catholic Faith.