Sorry Spud, you do know and cannot know this, because:
1. The earliest fragments containing the wording in this order are from about 300AD and you do not and cannot know how that relates to what was originally written.
2. Even if we assume the original had the wording in that order you do no and cannot know Mark's motivation in writing it in that order - indeed we don't even know who Mark was.
Further you are assuming he changed the order, therefore was basing his origin on earlier oral or written tradition with a different order - you have no evidence for this.
Actually, scholars are reasonably confident that they have got the order correct through textual criticism. The modern reconstructed Greek text is probably fairly close to the original.
It's normal not to have the originals or anything close to the originals for ancient texts. For example, there are no extant copies of Caesar's Gallic Wars from anything like as early as the fourth century.
We can't be certain of anything but it is reasonably likely that
- we have more or less reconstructed the original gospels
- Mark was the earliest with Matthew and Luke using it as the basis for their gospels
- we do not know who any of the authors are
- there are no other sources that can corroborate anything except the broadest details of Jesus' life
- dead men don't come alive again.
Actually, that last one is not "reasonably likely", it's pretty much a racing certainty. Any argument Spud makes has that mountain to scale. There is a hypothesis, for example, that Christianity was manufactured by Eusebius in the fourth century. This is a ridiculous theory with a load of huge problems
but it is still more credible than a man actually rising from the dead.