why having the proper authority to act in Gods name is important

Acts 19-20
Five ordinances that Paul Performed were
1.Baptism
2. Giving the gift of the Holy Ghost by the laying on of Hands (blessing)
3. Sacrament
4.He cast out evil spirits
5.Raised the dead (not sure if that is an ordinance)
When Paul found disciples he asked them if they had received the gift of the Holy Ghost, they said they hadn't heard of it, they said they were baptized as john had baptized and Paul explained that John baptized for repentance and he had prepared a way for Jesus.  He then baptized them with authority and blessed them by putting his hands on their head and they received the Holy Ghost and  were able to speak wonderful things. I found it interesting when Paul had cast out spirits they were gone but when others who claimed they had authority tried and the spirits said they didn't know them but they knew Jesus and Paul (Paul was ordained by Jesus, he was given the authority to act in Gods name).  The reason the disciples needed to be baptized again was because they needed to be baptized by one having authority by God to baptized so must everyone be baptized by someone who has been ordained with the priesthood as the apostles were ordained to baptize.
They then met on the first day of the week to break bread in remembrance of Jesus. The Sabbath day had changed from the last day of the week to the first day of the week because that was the day Jesus rose from the dead and Jesus also appeared to the apostles on the first day of the week.