@rajdude

Concerning the downloads link displayed in the menu:

It is only displayed when a set of photos is still valid to download, once there is no valid ssets to download the link in the menu is hidden.

If you hide the link using administration > Configuration > Menus like ddtddt suggested it will stay hidden.

The first time you try and hide this link you need to have a set of photos still valid for download or it will not appear in the list.

As for the error when you try to activate it, it is due to the plugins configuration that isn't checked before a user tries to activate the plugin.  I will commit a fix to github for this issue.