Meaning: return to an earlier position or decision.

Example:
After changing couple of jobs in last three years, Jane Stuart come full circle in her first company job.

Meaning: work at something but keep failing to make progress with it.

Example:
In the absence of adequate data, the surveyors are just going round in circles.

Meaning: to trigger a strong memory or feeling based on which there can be a mutual interest. To create an emotional response to something or a situation.

Example:
1.- The two immediately struck a note basis the fact that they follow the same faith. This has led to a beautiful marriage and a lifelong companionship.
2.- I usually cannot strike a chord with everybody but knowing that it can lead to some serious business opportunities, I can give it a shot.

Meaning: when a situation is urgent or desperate.

Example:
She's the person you would like to have around when the chips are down.