My post here opens imagepicker, rotates, resizes and uploads a user selected image when prompted by the site.
I had issues with upload despite files being created/rotated/resized. The linked solution that I figured out works (site dependent). The customwebviewer1.uploadfile needed an actual file path not the contenturi.
Download is tough and I'm not sure if I will figure that out as a lot of sites store stuff as blobs/base64 and not a direct link or file.
For the rest of the stuff you want, you will need to code it yourself. Eg, you grant permissions for the camera, when you click the site camera button, it opens camera, after picture taken, save the image (i would use a static filename), set a global variable to the image, upload the image.