True: there can be physical symptoms too, such as feeling constantly tired, sleeping badly, having no appetite or sex drive, and various aches and pains.

Yes, mental health can affect your physical health and vice versa.

They may be defensive or deny having a problem, but you should be empathetic and encourage them to visit a GP. You could always go with them if that helps.

False: when you're depressed you feel persistently sad for weeks or months, rather than just a few days.

losing control over how much you eat and then taking drastic action to not put on weight

False. Anyone can get an eating disorder, but teenagers and young adults are mostly affected.

https://www.nhs.uk/mental-health/feelings-symptoms-behaviours/behaviours/eating-disorders/overview/

anorexia nervosa (often called anorexia) – trying to control your weight by not eating enough food, exercising too much, or doing both.