What is the authenticity of the hadith: "Indeed, part of glorifying Allah is honoring the Muslim elder..." and what is the ruling on the word "ikram" (إكرام) in it with a dammah (ضمة), and are there similar hadiths in wording but different in vocalization (harakat) that are considered authentic?

The Hadith was narrated with two wordings: The first: "إن من إجلال الله: إكرام..." (Indeed, among the glorification of Allah is the honoring of...). In this wording, "إكرام" (ikram) is in the accusative case (mansoob) because it is the اسم إن (subject of "inna"). The second wording: "من إجلال الله إكرامُ..." (Among the glorification of Allah is the honoring of...). In this wording, "إكرام" (ikram) is in the nominative case (marfoo') because it is a delayed mubtada' (subject). In summary, the difference in vocalizations is due to a difference in grammatical parsing (i'rab), and this is something that Hadith commentators point out. There are specialized books dedicated to the grammatical analysis of Hadiths.