4a: Christian life is faith life. We live by faith, not by sight. Crucify flesh means to believe that my flesh (old man) is died on the cross with Jesus when Jesus was crucified.
Romans 6:6
“We know that our old self was crucified with him in order that the body of sin might be brought to nothing, so that we would no longer be enslaved to sin.”.
I cannot crucify myself. An external entity is needed to crucify me. In the case of Christians who believe in the crucifixion of Jesus Christ has already crucified with Him and they need to believe it and submit to Holy Spirit. Trying ourselves to be crucify our flesh is a worthless effort. Crucify my flesh means to believe in the death and resurrection of Jesus Christ and to submit to Him completely so that I will not fulfill my fleshly desires.
4b: The question "Can a person be a Christian without crucifying the flesh” is like asking "Can a person be called a "dead body" without being dead".
4c: The right Word is not preached in many churches. Christians remember the death of Jesus Christ and celebrate the resurrection of Jesus Christ every year. They remember it just as a historical event. But how many Christians realize that they were also died with him, and what they celebrate is the death of his own flesh (the old man) and his resurrection of his own new man, with the new identity in Christ? How many pastors teach that great hidden truth? Every Christian need to remember his death and resurrection every day and every moment and submit to the Holy Spirit to live the real Christian life.
Galatians 5:16
“But I say, walk by the Spirit, and you will not gratify the desires of the flesh.”