I so much appreciate this question and your concern over this child.  There are a few scriptural issues presented here, so let’s consider them separately.

WHAT DOES IT MEAN TO ASK JESUS INTO YOUR HEART? – While this term is not found in the Bible, many use it as a way to say that someone accepted Jesus Christ as their savior.  We read in Proverbs 23:26, “My son, give me thine heart, and let thine eyes observe my ways.”  Notice this desire for one’s heart is written to a ‘son’, so it is speaking to a believer, desiring the entirety of the heart.  In my life, in different Gospel messages, I have heard the plea many times for the unsaved to give their hearts to Jesus.  To make it clear, the way of salvation is for one to “believe on the Lord Jesus Christ” (Acts 16:31).  After that, the saved one should, indeed, give the Lord the entirety of his heart as we read in Mark 12:30, “And thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, and with all thy strength: this is the first commandment.”

IS BAPTISM PART OF OUR SALVATION? – NO! Baptism is an act of obedience for one who has accepted Jesus Christ as savior.  It is not a part of our salvation.  Only faith in the Lord Jesus can give salvation.  I encourage you to read Bible verses that show the way of salvation (John 3:16; Acts 16:31; Romans 10:9; Ephesians 2:8-9; Titus 3:5, etc.)  Notice that baptism is not mentioned in any of these verses that speak of how we can be saved.  Indeed, baptism is important and honors the Lord (Read Romans 6:3-6), but it does not save anyone. 

CAN OUR BEHAVIORS RESULT IN THE LOSS OF OUR SALVATION? – This is a question that many are unsure about.  Let us see what the Bible says about our salvation.

• John 10:27-29, “My sheep hear my voice, and I know them, and they follow me: And I give unto them ETERNAL LIFE; and they shall NEVER PERISH, neither shall any man pluck them out of my hand. My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father’s hand.”
• Romans 6:23, “For the wages of sin is death; but the gift of God is ETERNAL LIFE through Jesus Christ our Lord.”
• Romans 8:38-39, “For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come, Nor height, nor depth, nor any other creature, SHALL BE ABLE TO SEPARATE US from the love of God, which is in Christ Jesus our Lord.”
• Philippians 1:6, “Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ.”
• 1 John 5:13, “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.”

These verses, and many more, make it clear that the gift of eternal life that comes through faith in the Lord Jesus Christ, cannot be lost.  It is ours forever! The term ‘eternal life’ is used many times to describe those who know Christ as their savior.  Of course, ‘eternal life’ or ‘everlasting life’ refers to a life that NEVER ENDS.  For one to lose his/her salvation would go against the clear teachings of the scriptures.  It is saying that the life which cannot end will come to an end.  

I cannot say whether this young child truly accepted the Lord Jesus Christ as his savior.  Certainly, the Lord knows, as we read in 2 Timothy 2:19, “Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, Let every one that nameth the name of Christ depart from iniquity.”  The call for those who truly belong to the Lord is that they “depart from iniquity”.  If you have doubts about the salvation of this person, I urge you to sit down with him and go over the plan of salvation with him.  If he persists in saying that he is saved, you should remind him that as a believer, he should stop living a life of sin and seek to please the Lord with his life.  (CC)  (726.2)