(a)
(i) Paul admonished the Thessalonians not to grieve for the deceased as people without hope do. He said through Jesus, God will bring up those who have fallen asleep in Him.
(ii) Those who are alive will not precede those who are asleep.
(iii) The Lord will come with a cry of command coupled with Archangel's call and the sound of the trumpet of God and the living will join the dead in the clouds to meet Jesus.
(iv) Paul advised them not to be quickly shaken in mind in respect of the coming of the Lord as the day of the Lord will not come until a rebellion against God directed by the man of lawlessness comes to pass. He said He who now restrains it, will do so until He is out of the way and then the lawless one whose coming, by the activity of Satan, will be with power, pretension, signs, wonder and wicked deception, will be revealed. For those who are to perish and to those who refuse to love the truth and be saved, God will send a strong delusion to make them believe what is false. He who does not believe the truth but has pleasure in unrighteousness will be condemned.

(b) Some relevant lessons for Christians in the explanation of the Parousia are:
(i) Christians should avoid excessive grief for their dead.
(ii) Christians should prepare themselves and be alert for the second coming rather than speculating on when the day of the Lord would come.
(iii) Death is only physical, life continues after death.
(iv) Jesus will surely triumph over satan.