Check Box and Radio Button on Editable Selectable Grid

1) No

2) No

The only good news is that it's pretty easy to manipulate the saveInto of a paging grid such that only the last selection is saved, thereby accomplishing the effect of a grid with only 1 selection available.  

Appian's canned response is that you should just put validation on the grid to limit the number of selections, which is easy to do, but this is way too clumsy of an approach in many real-world use cases -- there really needs to be a built-in parameter to limit selections to X, which also disables the "select all" control under certain circumstances.  Until then, though, I just use code along the lines of the following in the saveInto of the grid:

a!save(
  local!gridSelection,
  a!gridSelection(
    pagingInfo: save!value.pagingInfo,
    selected: index(
      save!value.selected,
      length(save!value.selected),
      {}
    )
  )
)