I’ll offer a quick response to your question.
Roughly, you asked the following: Can I explain how the Catholic Church, if it was the church established by Christ as it claims to be, could possibly “backslide” when Jesus made several promises about His Church?
As for the promises: Christ has and will keep every one of those promises as they are properly understood. First, he promised His Spirit to guide the apostles into all truth. They deposited that truth to us in the sacred Scriptures and in their oral teachings in the apostolic age. **Wicked men, however, are capable of wresting the Scriptures, and so, when wicked men gain the ascendancy in the church, it backslides.
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Second, the church has the power to bind and loose insofar as it exercises ecclesiastical discipline, resolves theological controversies through authoritative judgments, etc. When it does this in accordance with the truth, then its decisions and acts are bound in heaven.
–Dan