Actually, you have this confusion just becasue you have an incorrect punctuation. The correct punctuation is "按 下面的 顺序 排列 " But "按下" would have different means in different contexts. For instance, "请帮我按下电梯（Please help me to push the elevator’s button）”, this sentence is a abbreviation of “请 你 帮我 按 一下 电梯的 按钮 ”. But in this sentence "他 按下了 按钮”, "按下"is a whole word, "了“ means the verb（按）is finished. As you known, there is no tense in Chinese, so the different positions of "了" in sentence would make differents tenses. It's very complex.
By the way, may I have a language exchange with you? I'm studying IELTS, and I want to improve my writing and speaking.