A person can know he is saved.
1 John 5:
10) He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son.
14) We know that we have passed from death unto life, because we love the brethren. He that loveth not hisbrother abideth in death.
13) These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.
Not sure about "most", but otherwise I agree.
True.
But when a person hears the gospel and believes it, he is sealed with the gift of the Holy Spirit, the guarantee of salvation (Eph 1:13-14).
This is where most people go wrong:
Matt 13:
3Then he told them many things in parables, saying: “A farmer went out to sow his seed.
4As he was scattering the seed, some fell along the path, and the birds came and ate it up.
5Some fell on rocky places, where it did not have much soil. It sprang up quickly, because the soil was shallow.
6But when the sun came up, the plants were scorched, and they withered because they had no root.
7Other seed fell among thorns, which grew up and choked the plants.
8Still other seed fell on good soil, where it produced a crop—a hundred, sixty or thirty times what was sown.
9Whoever has ears, let them hear.”
.....
18“Listen then to what the parable of the sower means:
19When anyone hears the message about the kingdom and does not understand it, the evil one comes and snatches away what was sown in their heart. This is the seed sown along the path.
20The seed falling on rocky ground refers to someone who hears the word and at once receives it with joy.
21But since they have no root, they last only a short time. When trouble or persecution comes because of the word, they quickly fall away.
22The seed falling among the thorns refers to someone who hears the word, but the worries of this life and the deceitfulness of wealth choke the word, making it unfruitful.
23But the seed falling on good soil refers to someone who hears the word and understands it. This is the one who produces a crop, yielding a hundred, sixty or thirty times what was sown.”
Many will hear the gospel in fact almost everyone in the world has heard the gospel but still many will faill including some that initaially believed.
Daniel 11:
33“Those who are wise will instruct many, though for a time they will fall by the sword or be burned or captured or plundered.
34When they fall, they will receive a little help,
and many who are not sincere will join them. 35Some of the wise will stumble, so that they may be refined, purified and made spotless until the time of the end, for it will still come at the appointed time.