Welcome on the forum [:)]

1. At the two highest quality levels, the transparency of walls is ignored.

2. No, Sweet Home 3D doesn't support transparent sky and ground in resulting PNG.

3. You should use 3D view > Virtual visit to place the point where you want.

3b. To move all the objects at all levels, choose Edit > Select all at all levels first, then drag and drop objects with mouse or use keyboard arrows. You may use also AdvancedEditing.sh3p plugin listed here.

4. Select Searchable list option in preferences.