"Because my plan does not allow me to correct last year's contribution anymore, I hope to get a full understanding on what are my options and and what are each tax implication for it."
If you are referring to an excess elective deferral made for 2024, as @DanaB27 said, the deadline to obtain the corrective distribution is April 15, 2025. Because this deadline has not yet passed, your current employer should cooperate with your request to make the return of excess contribution.
