When did this verse apply?<quoted text>
Unbelief, not disobeying. That's a good start. And that is what Romans 11 is all about. If one doesn't believe then obeying does not matter. However if one believes, that one has a desire to obey. Moreover, none of us are able to completely obey while we still live in a corrupt vessel.
I have stated in the past that most of the gospel accounts and the first part of Acts were written to the Jews but some passages in them are to all people.
The Gospel is now open to anyone who believes (both Jew and Gentile) in the finished work of Jesus on the cross. Those who truly believe (not just say they believe because anyone can say "I believe" even if they don't) have had their eyes opened by God, and this is not exclusive but inclusive. I have never had the power to open my own spiritual eyes. That is left up to God.
"to the Jew first and then the Greek." Well chapter 11 of Romans goes on to explain that God, has blinded the Jews because of their unbelief, but He is not finished with them yet. He will complete that work when the full number of the Gentiles has come in. In other words, when this age ends, He will again deal with the Jews.
The Bible clearly states that salvation is a work of God. He is the author and finisher of our faith. We didn't start it nor can we finish it.
Now, do you believe that all who claim to be "Christian" are believers? Do you believe that all who claim to be "Christian" are saved? Do you believe that all who say they believe truly believe?
 For if you forgive men their trespasses, your heavenly Father also will forgive you;
 but if you do not forgive men their trespasses, neither will your Father forgive your trespasses.
Could the Jews before the sacrifice be forgiven simply by forgiving others and if not why doesn't it still apply today? And if so, why would they need the sacrifice?
I can see where you are going with the other question and that is to say now the gospel is open to both Jew and Gentile where it wasn't before so now salvation is the same for them where it wasn't before. I disagree but I will understand better where you are coming from if you address the verses in Matthew as that is what it was all based on including asking about salvation being the same. I believe those verses show the teachings of Christ have always applied to everyone and still do but if you can address the questions asked about Matthew 6 I would appreciate it. Thank you