Which one is correct? Or are all of them correct? Can about and around be used interchangeably?
In all these cases, you can use either form and it will be correct. Around is used exclusively in these verbs in the US and Canada (I daresay). About is more common in Britain and maybe Australia and Ireland, but I can't be too sure. However, they can definitely be used interchangeably, although if you wish to "localize" your text for the States specifically, you would naturally go with around.
"around" and "about" after verbs of movement
1 to walk around a small town - that is a circular movement at the outer edge of the town
2 to walk about the town - that means going to various places without a definite destination. Maybe it is a newcomer who wants to get to know the town. In my view It should be "to walk about in (the) town" and I think "in" was omitted long ago. But I don't know whether mother-tongue speakers would agree.
"around" and "about" indicating position
3 Papers were lying around the table on the floor.
4 Papers were scattered about the room on the floor.
In 3 the papers are lying in a circular line enclosing the table. In 4 the papers are lying on the floor at various places.
These are only two uses of the two prepositions. But both of them have various uses and in some uses they are overlapping.