In general, eagle lecterns allow more teleportation tablets to be created, while demon lecterns allow more enchantment tablets to be created. To make both types of tablets, 2 studies with 2 different lecterns are required.
Crystal balls allow players to change the element of their elemental staves, battlestaves or mystic staves depending on the type of crystal ball built. Note that the changing of elements for battlestaves and mystic staves require a rune cost.
Just like in a real house, if the telescope is blocked by another room in the house, it will not work and your character will say, "What's this? A close up of a wall," though if a roof is mostly blocking its view, no problems will arise.
If you wish to move this room, you may visit Varrock museum and ask for a new plinth. When you replace the room and add this new plinth your statue will be restored to its previous state. You cannot build a second statue in another room, even if you completed the first one.
Removing the statue plinth itself will result in a loss of all progress with it.