Does Satan understand the plan God has designed and what is to come? If so, why does he wait to carry out these actions instead of acting now on his desire to ruin God's plan?
To understand Satan’s work, we should first remember that God is always in control of all things, including Satan’s actions. As we can see clearly in the book of Job, Satan cannot act to cause harm without God’s allowance. Secondly, Satan is a created being, so he is limited by his nature and abilities. He is not omnipresent nor is he omniscient. Finally, as a fallen creature, Satan is a prisoner of his own sinful nature, leaving him unable to understand God’s word or to act in any manner other than opposing God’s will.
Therefore, Satan cannot understand the plans or purposes of God beyond a limited degree, since he cannot understand scripture. In fact, the reason so much of scripture is taught through parable or prophecies with obscured interpretations is to thwart Satan’s ability to understand and interfere with God’s plan. Only those to whom God grants the ability to understand scripture will know the future. To the rest - including Satan - the truth remains out of reach.
Finally, God is preventing Satan from taking steps too early, in keeping with God’s timing. For example, Satan would prefer to raise up an antichrist at any time, but God is restraining Satan until the church has been removed from the earth at the rapture. Paul says:
So Satan is largely unaware of what God plans to do, and his own plans to disrupt creation are managed by the Lord to ensure it falls within God’s purposes and timing.