Some translations set each line of poetry farther to the right than the rest of the text to make it easier to read. The ULB does this with the poetry that is quoted from the Old Testament in 4:25-26.
The first Christians wanted very much to be united. They wanted to believe the same things and share everything they owned and help those who needed help.
This phrase refers to things that only God can do. The Christians wanted God to do what only he can do so that people would believe that what they said about Jesus was true.
The cornerstone was the first piece of stone that people put down when they were building a building. This is a metaphor for the most important part of something, the part on which everything depends. To say that Jesus is the cornerstone of the church is to say that nothing in the church is more important than Jesus and that everything about the church depends on Jesus. (See: [[rc://en/ta/man/jit/figs-metaphor]] and [[rc://en/tw/dict/bible/kt/faith]])
"There is no other name under heaven given among men by which we must be saved" ([Acts 4:12](../../act/04/12.md)). With these words Peter was saying that no other person who has ever been on the earth or will ever be on earth can save people.