Pink lines/Dot - what does it mean?

There are a few things that I can think of, which you can check:

• Is the instance locked?
• Is the instance inside of a frame that has autolayout?

You can drag the dot to rearrange elements in your selection. Moreover, you can use the dot to select multiple layers and rearrange the whole group

Adding to this, the lines show the spacing between elements, which can be changed in the right toolbar (In Xd you can only change these by dragging, so that might cause confusion)

You probably cant move them around because they are in a parent ‘auto layout’ frame.