How do I center all the frames?

[anto]

I am creating a book of poems. I have spreads. 
1. How do I center the frame using a keyboard shortcut?
2. How do I replace a double click on one of the frame nodes with a keyboard shortcut?
3. How to select all frames and center them all at once.

[anto]

I think I have solved the fourth problem. But it applies to only one page. To immediately center the frame, you need to hold down the CTRL button while clicking on the node on the right side.

But there was problem 5.
When I click on a node, the frame does not shrink to the last longest line, but randomly changes the width of the frame. How can I fix it?

[PaulEC]

30 minutes ago, anto said:

When I click on a node, the frame does not shrink to the last longest line, but randomly changes the width of the frame. How can I fix it?

Click on the bottom node instead of a side node.

[anto]

7 minutes ago, PaulEC said:

Click on the bottom node instead of a side node.

But then I can't center it. Do I need to press a side knot after the bottom knot?