In 1 Cor. 10:4 the Holy Spirit indicates the rock of the OT was Jesus Christ.
In Matt. 16:18 the Holy Spirit indicates the rock upon which the church will be built can be seen as Peter. Given that the Holy Spirit through Paul in Ephesians indicates the apostles are the "foundation" upon which the church is built, and given that the Holy Spirit in Isaish terms Abraham "the rock," I don't see why I should understand the Holy Spirit differently as to this verse.
No, He didn't. I thought we went through this already. Maybe it was with someone else. Anyway, Isaiah 51:1 is calling the Lord the Rock. In verse 2 it goes on to say "and unto Abraham".