Are we to obey the whole Bible?
We know God expects and demands obedience, Exodus 19:5. We are told in II Timothy 2:15 to study and rightly divide the word, otherwise we could get confused on what to obey. Adam was told not to build an ark and Moses to save God's people.
There are three dispensations or time periods how God dealt with people. The first is the Patriach Age, where He spoke to the heads of families, like Abraham. The second is the Mosaic Age where God gave the Ten Commandments on Mt. Sinai to Moses and there was a lot more to the old law, read Lieviticus. We are so blessed to be under the third one, the Christian Age, notice the thief of the cross died under the old law as the Christian Age didn't come into effect until the death of Christ, Hebrews 9:16. While Jesus was alive He could forgive sins and did many times and the final time was the thief. We are now under Christ and must become a Christian to be pleasing to God, Acts 11:26, 26:28 and I Peter 4:16.
There are ten examples on how to become a Christian in the book of Acts. God has put them here and there to make you search the scriptures to find the truth, that is how we tell if something is a lie! Jesus said so in John 5:39 and the Bereans received the word and searched the scriptures daily whether those things were so, Acts 17:11.
Do you know who preached the first gospel sermon and the day when God first added the saved to the church?