Is the name "Khalid" forbidden on the basis that immortality belongs to Allah alone? Thank you.

It is permissible to be named Khalid, because the Prophet, peace and blessings be upon him, approved this name for one of his companions, and it is known that he would not approve of falsehood, and that he used to change names that contravened Islamic law. The 'eternity' (khulūd) here is relative. The Permanent Committee for Scholarly Research and Ifta' has affirmed the permissibility of this naming.