squeaking could be because of the brake pads being worn.
brake pads have a a layer of friction material at the bottom that produces a squeak / squeal as they get low, this serves as an audible warning to the driver that the pads are low and could need replacing.
You should take the wheel off and have a look at the pads, you need to check the inside pad as if the slider is sticky you will wear the inside pad more than outside, so check the inside pad particularly. if one set is worn out you will need to replace both.
brake discs require more experience to know if you need to replace them, as they get thin they will lip badly on the top of the disc, so you will need to know to recognise this, or any fatigue / cracking in the metal, to know when to replace the discs.
As for derv sound, have you checked your oil level recently? Do you keep up the service history? If the car has done more than 36k miles or 3 years without cambelt change realistically this could do with replacing, at which point you typically do the variator, often associated with a derv sound. I not 100% if that applys to JTS engines but believe it does.