The different colored patch on the handset is an easy clean silicone feature that prevents carbonate build up and stops the shower from becoming clogged up.
Yes; the hand shower is adjustable along the rail and also detaches from it's holder?
Not necessarily. You could use something like this as a simple shower that could be connected to a tub mixer or connect it to a manual valve for a cheap and esy to install alternative.
You can use it with every single Hudson Reed Concealed Shower Valve we sell. You can even use it with your exisiting installation as long as you're working with standard NPT pipework.