The three questions pertained to both applications of the prophesy. They asked....
“Tell us, when will these things be, and what will be the sign of your presence and of the conclusion of the system of things?”
The last part of the question was thought to be imminent....."the conclusion of the system of things" or "the end of the age". Jesus gave them the signs to watch out for.....but he did not tell them "when" they could expect the time of his "presence" ("parousia" does not mean "coming")
The time of his "presence" and the time of his "manifestation" are two separate events.
After the outbreak of the coming "great tribulation" Jesus foretold....
“Immediately after the tribulation of those days, the sun will be darkened, and the moon will not give its light, and the stars will fall from heaven, and the powers of the heavens will be shaken. 30 Then the sign of the Son of man will appear in heaven, and all the tribes of the earth will beat themselves in grief, and they will see the Son of man coming on the clouds of heaven with power and great glory. 31 And he will send out his angels with a great trumpet sound, and they will gather his chosen ones together from the four winds, from one extremity of the heavens to their other extremity."
This has not happened as yet....
but Jesus has been "present" for the entire time since his enthronement as King in 1914 when the sign of the last days of this present system began.
No man witnessed Jesus' enthronement because it was in heaven. Daniel however was given a vision of that future event. (Daniel 7:13-14) The entire book of Daniel is referencing "the time of the end" and Daniel was told to seal up his book as none of its contents would be fully understood until then. (Daniel 12:4)
This also coincides with the time the devil was confined to the earth to carry out his last attack on God's worshipers in this system. (Revelation 12:7-12)
The devil is no longer subtle....since that time all his efforts have been very concentrated, so that now, as we near the finale, his world is completely saturated with immoral sex and violence and demonic entertainment. Everything in this world is designed to enslave humans in one way or another and take them away from God. They have been convinced either that they don't need him...or that he doesn't exist.
As Jesus was leaving this earth for the last time, the apostles asked....
“Lord, are you restoring the kingdom to Israel at this time." (Acts 1:6) It is apparent that they thought that the coming of God's kingdom, which they believed involved fleshly Israel and a re-establishment of God's people as a free and independent nation again under their liberator and King....this was foremost was in their minds. (Suffering under Gentile domination was not easy.) This is what the Messianic prophesies indicated.....but their expectations were not fulfilled at that time.
This is one of the reasons why Jews rejected Jesus as Messiah.....they got the timing wrong. But faith would lead Christian worshippers all the way to the 21st century. In this "time of the end" knowledge would become "abundant" and the ones who were open to the operation of God's spirit were granted understanding and insight into many things. (Daniel 12:4; 9-10)
These 'cleansed and refined themselves' spiritually, removing the stain of false doctrines that had been introduced by an apostate church centuries before. They then got busy 'preaching the gospel of the kingdom' (Matthew 24:14) and making disciples, teaching them the truth as Jesus had instructed them to do. (Matthew 28:19-20) He promised that he would back this work.....and he did. It was to be carried on right to the end.
Knowing where we are in the stream of time is important because Jesus said that his coming would be like
"a thief in the night"....unexpected by the majority. Only his true disciples would be prepared like the 5 wise virgins of Jesus parable who had oil in reserve to reignite their lamps when the bridegroom delayed. (Matthew 25:1-13)
Will You “Keep on the Watch”? — Watchtower ONLINE LIBRARY
I believe that we are living in the outworking of this prophesy.