Q2. How to achieve this :
when I edit, it pops up the form with the 3 items being editable and able to save. Even if I use that default edit button, it only allows me to edit the Name/TItle only.
If you are using a Collection, then the default action on each item (Post) will be to show details screen for that item. You can configure the details screen as you wish. Add or remove components using the left hand panel in the builder.
You can configure the Edit Form. Again, add or remove components using the panel on the left.