The bottom line is, did the apostles obey Jesus commands? Absolutely!
And Jesus did give them commands of how to set up the New Testament Church.
And Peter summerized the One Plan of salvation in
Acts 2:38 And they obeyed the gospel all through the book of Acts, the only book in the Bible that tells us how to be saved.
The Four Gospels, is not the gospel. It is te life of Jesus
Acts tells us how to be saved.
The Letters tells us how to let the 'fruit of the Spirit" come forth.
There is only One Gospel,as Paul tells us,...
Galatians 1:6 I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel:
7 Which is not another; but there be some that trouble you, and would pervert the gospel of Christ.
8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
9 As we said before, so say I now again, if any man preach any other gospel unto you than that ye have received, let him be accursed