What is the ruling on standing up for an arriving person, an elder, or a guest in Islam? Is abandoning these customs considered a defect and a lack of manners? And to what extent is there an excuse for observing these customs?

There is no legal impediment to dealing with the customs of a people, as long as they do not violate the Sharia. Indeed, it is affirmed to act upon them if they increase affection, love, and social cohesion. As for standing for a guest or an elder, some scholars have held it to be commendable if it is for the purpose of honoring, and this is the most preponderant view, while others have held it to be disliked.