If a person denies Jesus, he immediately loses his salvation.
But, he has until he dies to repent of his sin of denial. If he does not repent before death, Jesus will then deny him before His father.
Peter repented of his sins and he asked for forgiveness; otherwise Jesus would not have forgiven him.
Jesus saves every person who repents and believes in Him.
What must a person do in order to continue in his faith in Jesus after he has been saved by Jesus?
Nice try but you ignore that last verse I posted which is why all you excuses above are meaningless.
by which you are saved, if you hold it fast—unless you believed in vain. rsv
by which also you are saved, if you hold fast that word which I preached to you—unless you believed in vain. nkjv
How do you think a person "holds fast"?
How do you think a person "believes in vain"?
Before the foundation of the world, God placed into His hand the people who He knew would still be faithful/obedient to His commandments at the time of their death. That is why these faithful-until-death people cannot ever be taken out of His hand.
We Christians do not know for sure who these faithful-until-death people are, but God knows!