I once asked a Catholic priest how I could be assured salvation and heaven. He stammered for a bit before saying, "Well, that is a Great Mystery."
Don't think so.
If anyone sees his brother sinning a sin which does not lead to death, he will ask, and He will give him life for those who commit sin not leading to death. There is sin leading to death. I do not say that he should pray about that. 17 All unrighteousness is sin, and there is sin not leading to death. -- 1 John 5:16-17, NKJV
"Leading to death" is pros thanatos in the Greek. It's absolutely reasonable to translate "pros thanatos" as "mortal".