返る and 返す: an item coming back and returning it
Compare money or objects coming back with returning them, and distinguish going home with 帰る from replying with 返す.
Money and items coming back
預けたお金が返ってきました。 says that money previously deposited or entrusted has come back. 返る, read かえる, becomes 返って, with the returned money as subject.
貸した傘がまだ返っていません。 says that the umbrella lent out has not yet been returned. Lack of return does not establish that the borrower lost it.
Return something to its source
友達に借りた本を返しました。 says that someone returned a book borrowed from a friend. With 返す, read かえす, the book before を is the returned object.
明日までに鍵を受付に返してください。 asks someone to return the key to reception by tomorrow. までに gives the deadline, and 受付に gives the return location.
Replies and going home
質問に答えを返しました。 means that someone sent back an answer to a question. 返す can describe a response, not only returning the exact same object.
仕事が終わったので、家に帰ります。 means that the speaker will go home because work has finished. Going home uses 帰る, with the same reading but a different spelling from 返る for returned money.
Has the lender received the umbrella back in 貸した傘がまだ返っていません?
Show the answer and why
Not yet. まだ返っていません describes a return that has not happened and does not establish whether the umbrella is lost.