What is the ruling on bowing to elders in a manner that differs from ritual bowing (rukuʿ) and prostration (sujud), and is it permissible in Islam?

It is forbidden to bow, prostrate, or prostrate to anyone. The Messenger of Allah, peace and blessings be upon him, disliked the Companions standing for him and forbade bowing to greet a brother or friend, permitting handshaking instead. As for kneeling before a sitting person rather than a standing one, there is no harm in it if it is devoid of glorifying that person, and this occurred among the Companions before the Messenger of Allah, peace and blessings be upon him.