There are several things we can learn from our Obadiah passage.
The first is a theme that is a very common one, and that is that God is sovereign. If He wasn't, He couldn't promise Judah that Edom would receive judgment. But He is and He did.
Pride is deceptive (v3) and results in destruction. Both proud individuals and proud nations will reap what they sow.
The good news is that God has made a way of escape from wrath in the salvation provided by Jesus Christ, and one day He will rule the entire earth.
In our Acts passage we see that Simon appears to accept the gospel, but in the end he does not seem to have truly repented and believed.
People can respond favorably to the gospel without becoming genuinely saved. Sometimes they are attracted to the message itself, or to the fellowship, or the tradition, or fear of judgment.
It is impossible for our to know, at the outset, if someone's conversion is genuine. And it is not our job to determine it - we are to treat them as genuine believers. However, saying you are a Christian, doesn't make it so, and eventually such a profession is proved false by open sin and lack of repentance. Of course perfection is never possible - but there should be evidence of God's goodness and progress in our lives.
Tomorrow's Bible In a Year Passage passage: Ruth 1-4; Acts 8:26-40