"He was chosen before the creation of the world, but was revealed in these last times for your sake." NIV translation
Jesus' sacrifice for us did not catch God by surprise and Jesus wasn't His plan B. We see here that, even before the creation of the world, God's plan for saving us involved Jesus dying in our place.
"Through him you believe in God, who raised him from the dead and glorified him, and so your faith and hope are in God." NIV translation
Jesus' coming to the earth, dying for our sins, and being raised again demonstrates the Father's love and power. Our hope is that the Father will do the same for us just as Jesus promised and, as we have already seen, He gave us the Spirit to testify to our spirits that we are His.
"Now that you have purified yourselves by obeying the truth so that you have sincere love for your brothers, love one another deeply, from the heart." NIV translation
A pure heart comes from knowing the Word of God and putting it in action. The Spirit tells us when our actions and words do not match what God's Word says. The Spirit will also give us the power to conform our lives to that Word. The more we are transformed by the Word (Jesus Christ), the more we will show love to others and it will be from the heart.
"For you have been born again, not of perishable seed, but of imperishable, through the living and enduring word of God. For, 'All men are like grass, and all their glory is like the flowers of the field; the grass withers and the flowers fall, but the word of the Lord stands forever.' And this is the word that was preached to you." NIV translation
Peter ends this chapter with a quote from Isaiah 40. He uses it to let us see that all of the earthly stuff will die and that is why it is important that we be born again. In the previous passage, Peter called us to love our brothers and that is not possible on our own but only through the power of God. To receive that power, we must be born again by accepting Jesus as our savior. Then we are no longer perishable seed but now are imperishable and have the power to love.