Took three weeks
Worth saying it was not quick, closer to three weeks than one. The handset itself is solid and heavier than I pictured, which I liked. Order early if it is a gift.

It wedges between your ear and your shoulder and stays there. That is the whole product, and it is the bit you cannot do with a flat piece of glass.
Turn your phone over and look at the socket on the bottom edge. An oval slot means you want the USB-C. A small round hole means you want the 3.5 mm. Pick the matching one on the product page.
No. There is no battery to run flat and no app to install. It hangs on the end of a cord, which is the whole idea.
It is the size of a handset off an old house phone, and it has the weight to match. The cord is coiled, so it sits short and pulls out when you need it to.
Only the colour. White is the one that sat in half the hallways in Britain. Topaz yellow and aubergine are for people who want it to look like 1986 on purpose. The cord always matches the handset.