Yes, there is a device for that.

Yes, ours is tight so far. Even with the current heavy rainfall.

Yes, I bought this last summer and it has held up really well. Hope this helps.

Yes, there is a place formğaflıck but you need to buy it separately.

The box is weatherproof, but not 100% waterproof. This means that in case of heavy rainfall, a penetration of small amounts of water cannot be prevented. For the wood to "breathe", stowing it in a closed container may not be optimal. Otherwise we would have wooden shelves, https://www.galaxus.ch/de/Search?searchSectors=0&q=holzregal

Inner dimensions Length 114.5cm Width 47.5cm Height 52cm

No it doesn't come assembled, but is pretty quick to put together :)