The only way to become saved in my opinion is TRUELY accepting Jesus into your heart.
If by accepting Him into your heart you mean having faith in Him and obeying Him, then I agree.
Admitting you are a sinner and believing Jesus was the son of God and was sent to earth to cleanse us from our sins.
It is a complete turn from sin.
Well, I think all of us resolve to sin no more, but we end up failing now and then. Good thing we can ask for God’s forgivenness and He will give it to us ,if we have a contrite heart of course (this happens through the Sacrament of Reconciliation us Catholic believe.)
I also believe that once you are saved you are always saved.
I would agree here and say that I understand that to mean once you go to heaven you won’t leave. That being said, I believe it depends on the state of your soul at death as Jesus tells us “He who endures to the end will be saved” (Matt. 24:13) Also, Paul warns, “See then the kindness and the severity of God: severity toward those who have fallen, but God’s kindness to you, provided you continue in his kindness; otherwise you too will be cut off” (Rom. 11:22).
Likewise, Paul writes “I am not aware of anything against myself, but I am not thereby justified. It is the Lord who judges me” (1 Cor. 4:4). He also worries about falling himself: I pummel my body and subdue it, lest after preaching to others I myself should be disqualified" (1 Cor. 9:27).
If my soul is in a state of grace when I die, I will be saved. If it is in state of rebellion against God (mortal sin) then I will go to Hell. So until then, I will have faith in Jesus and firmly resolve to obey Him and I hope with confidence that I will persevere.