YES! Even though we have a non-free option to remove watermark from downloaded video. You don't have to use it because you can achieve the same purpose by collecting likes from Facebook.
By default, slideshows are stored as html elements, which require relatively higher hardware spec, thus the replay may be slow on some mobile devices. By downloading it as a video file, you can get consistent replay experience on all devices. Meanwhile, you can post it to more popular sites such as Youtube.
Only slideshow owner could request for a download. To request for download, go to Account Manage page, find the work that you want to download, click request button near HD video or SD video field.
Click "Account" at top menu. You can sign-up with email and password, sign-in with your Google account, or create guest account with "Try as anonymous user" option.
Currently the application does not support caption editing. However there are many handy photo editing softwares that support caption. You can use them to implant captions in photos. By adding captions word by word and saving a copy at each step, you can even enable caption animation in slideshow.
If you use background music, slideshow length is always equal to music length. You can use other tools to trim audio to the length as needed. If no background music, you can set duration in "Load Music" dialog box.
iOS does not allow user to load audio from browser. In such case, you have to load online audio from web.
No. The editor resizes images automatically at uploading, and its output resolution is always no larger than 1440 x 1080. Therefore higher resolution does not help if its active portion (the portion that is shown in slideshow) has more than 1440 pixels in width or 1080 pixels in height.
On the other hand, large files dramatically slow down image load speed. We suggest to resize images to proper size before loading it.
Canvas is a new feature of HTML5. It acts as backstage for slideshows. Although all modern browsers support this feature, you will get above message if using IE8 or older version. We suggest to update browser to IE10 or higher, or use Chrome instead.

For more information, see Pholody blogs with User help tag.