rename gives a column a different name and changes nothing else. The new name goes first, the way assignment reads and the way every other verb that makes a column already works. If you are arriving from pandas, read that pair twice: rename(columns={"old": "new"}) is the other way round, and both spellings are legal here.
drop_duplicates drops rows that are identical across every column. The answer comes back in a settled order, because dropping repeats says nothing about which order the rest should be in, and an answer that reorders itself between runs is not predictable.