The gift of prophecy is the gift of God-inspired speech.
     It may deal with past, present, or future, for God is not limited! But the content or meaning of the words does not define the nature of the gift, as some unfortunately teach.

The various gifts of the Spirit are simply the supernatural methodologies of the Spirit expressed through individual people of God. The method/gift of the Spirit does not define the specific content of its function.

word 'prophesy' in our Old Testament is נבא (nâbâ) which means simply 'inspired speech' and nothing more; and so this could either be in song, in worship to God, in addressing people directly, or in any other situation when the human voice is directly inspired by God. So, as the word 'to prophesy' simply means inspired speech, you can prophesy in a prayer, or in a teaching, or in a rebuke, or in any way which the Holy Spirit chooses, but it is the inspiration/source of the actual words which make it a prophecy.

The fact that we today use the English word 'prophecy' to mean prediction does not alter the meaning of 'to prophesy' in Holy Scripture. The Bible is full of examples of prophecy – the whole book of Psalms, for instance.

the Bible also teaches that there is a limit on the number of persons being used in this paricular gift in the same meeting of a congregation.

Because no single kind of gift is to dominate the whole meeting if there is to be a balanced ministry of the whole Body of Christ within a particular gathering.

Unfortunately, the current tendency for a Christian meeting to be largely a hymn-sermon-sandwich contradicts this principle.

what if two persons are both inspired of God to speak. Who should then speak first?

It does not matter. The important issue is that there be no competition in that regard.

If someone had been holding back because of shyness, or for whatever reason, and then, while someone is already speaking, begins to speak. The right of the first speaker already speaking is irrelevant. It is only the welfare of the hearers that matters, so the Bible says that first must be silent.

things 'decently and in order' does not refer to a approved program but to the interests of the recipients of the ministry of the Holy Spirit, delivered through the gifts distributed among believers.

It is for this reason that love is the absolute conditioning factor in all inspired ministry. So, remember –

would not need to be said unless there were times and situations among God's people in which it would be easy to do just that!