Hmmm, I'll try to answer your questions, but I'm an old woman, not a Pastor.
Baptism, original word baptisma, bap'-tis-mah used 22 times in N.T.:immersion, submersion.
Christian baptism; a rite of immersion in water as commanded by Christ, by which one after confessing his sins and professing his faith in Christ, having been born again by the Holy Spirit unto a new life, identifies publicly with the fellowship of Christ and the church.
John 3:23 seems to suggest that John the Baptist was baptizing by immersion, since he chose the location "because there was much water there."
"And John also was baptizing in Aenon near to Salim, because there was much water there: and they came, and were baptized." John 3:23
Apollos taught the baptism of John. Aquila and Priscilla took him aside and explained the way of God to him more accurately (Acts 18:24-26). Acts 19:1-5 clearly shows that there is a difference in the baptism of John and the baptism that puts one into Christ.
Acts 2:37-41 - ... they were cut to the heart, and said to Peter and the rest of the apostles, 'Brethren, what shall we do?' And Peter said to them, 'Repent, and be baptised everyone of you ... for the forgiveness of your sins; and you shall receive the Gift of the Holy Spirit ... So those who accepted His Word were baptised.
Acts 8:36-39 And as they went on their way, they came unto a certain water: and the eunuch said, See, here is water; what doth hinder me to be baptized? And Philip said, If thou believest with all thine heart, thou mayest. And he answered and said, I believe that Jesus Christ is the Son of God. And he commanded the chariot to stand still: and they went down both into the water, both Philip and the eunuch; and he baptized him. And when they were come up out of the water, the Spirit of the Lord caught away Philip, that the eunuch saw him no more: and he went on his way rejoicing.
Ro 6:4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
Verses such as Romans 6:4-5 and Colossians 2:12 compare the Christian's baptism to the death and resurrection of Christ. In many modern people's minds, immersion seems to better mirror this picture.
As a wedding ring is an outward profession of marriage, but not marriage itself, so baptism is the outward profession of salvation, but not salvation itself.
I would have to conclude from Acts 2:38 that baptism is necessary for salvation (repentance + baptism = remission of sins). Another verse to consider is Mk.16:16 - "He who believes and is baptized will be saved" (belief + baptism = salvation).
It's a picture, an illustration.
Everyone has questions that they can only search to their satisfaction by their own efforts. Look into it for yourself. Come to your own conclusions. That's what I do.
In Christ,
How does one get into Christ?
W.S.