1)Even I am facing a similar issue. Either the graph displays as shown above or does not display at all. Axes are visible but not the data read by the sensor.
Did you try the link https://www.boltiot.com/workshop-content-beta.php1?
2)I am also facing other problems with cloud. Even when I upload a normal LED controller page, it does not work when accessed from the cloud. It only works when I access it using the ip address of bolt.
Please share your code. Note that the commands are little diffrent when you access via the cloud.
3)What is in the file bolt.html? I accidentally set the page for device type 'bolt' to some other file and now I am not able to see bolt.html in the dropdown list. Can I get the bolt.html file again?
Not sure what ut includes. But if its not particularly useful then I suggest you ignore it.
4)How to delete uploaded pages which we are no longer going to use?
You cannot delete them as of now. You can replace them tough. Just upload a file with the same name to replace.