I've just double checked and apparently the transparency lock feature was not removed from the list during editing, we're going to correct the page. The sticker spray image will also be adjusted so that it matches the text to the right.
When you save a file on Android it is saved in standard PTG format so if you copy it over from the file system on your device (in the AndroidPaintings folder) to a desktop machine you can edit it there with all the layers intact. You can also send PTG via email if you choose the Export option from the menu.
The Android version doesn't support transparent canvases currently so PNG exports of the entire painting won't be transparent.