Was Jesus Christ immortal when he died?

Yes. And I could give you the exact same answer if you asked the question again but dropped the second "t" in that sentence.

Proverbs 8:22-30 tells of the Lord’s existence before the Creation, which is confirmed in Micah 5:2 and John 1:1-2, and His participation in the event.  And long before the foundation of Earth was laid Jesus agreed to be born as a man to die for the sins of the people (1 Peter 1:18-20). So we know He was God (spirit only) at one point.

He gave up His throne in heaven to be born as man. And He died as man. His body was mortal, His spirit eternal. At the crucifixion His body died while His spirit continued on.

When Jesus came out of the grave He was still a man. He even had the disciples touch Him to verify that He was a physical being, not a spirit. (Luke 24:39) But His body was now immortal. What all this shows us is that even though believers in Jesus Christ may die physically, our spirits will never die and one day our bodies will be resurrected to become immortal as well.

Acts 1:9 says Jesus was taken up (into the sky) before their very eyes. Since our eyes can’t see spiritual beings and since Jesus was in physical form just before He ascended it’s logical to assume He was taken up in physical form. Years later when the Lord visited John on the Isle of Patmos he looked “like a son of man” meaning He was in human form (Rev. 1:12-13). And later, when John was taken to the Throne of God, he saw a lamb as it had been slain (Rev. 5:5-6). One of the elders identified Him as Jesus. Scholars interpret the phrase “as it had been slain” to mean that the Lord was still in the form He was in when He died, the form of a man. When Jesus agreed to become a man, it was a forever decision.

No, but he was immortal 3 days later.

His Spirit is infinite and immortal and his body is finite and mortal.

He was immortal in his resurrected body..

His body wasn't but his soul is.

Yes and no.

3 days dead, he was!

No.