Explanation:

- "Through thick and thin" typically means being supportive and loyal, no matter what. It implies staying committed under all circumstances, whether they are good or bad.

- Option 1: "With humility" means with modesty and without arrogance. This doesn’t relate directly to being loyal or adjusting to circumstances.

- Option 2: "With ego and pride" implies acting with a sense of superiority or confidence. This is unrelated to the consistency implied by the idiom.

- Option 3: "With all kinds of people" means interacting or dealing with different people, which doesn’t directly connect to the idiom’s meaning of enduring varying situations.

- Option 4: "Under all conditions" is the correct meaning. It reflects the idea of staying steadfast through different scenarios, both positive and negative.