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.
Matt. 13:10 And the disciples came and said to Him, “Why do You speak to them in parables?”
Matt. 13:11 Jesus answered them, “To you it has been granted to know the mysteries of the kingdom of heaven, but to them it has not been granted.
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:
2Th. 2:6 And you know what restrains him now, so that in his time he will be revealed.
2Th. 2:7 For the mystery of lawlessness is already at work; only he who now restrains will do so until he is taken out of the way.
2Th. 2:8 Then that lawless one will be revealed whom the Lord will slay with the breath of His mouth and bring to an end by the appearance of His coming;
2Th. 2:9 that is, the one whose coming is in accord with the activity of Satan, with all power and signs and false wonders,
2Th. 2:10 and with all the deception of wickedness for those who perish, because they did not receive the love of the truth so as to be saved.
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.