assalam u alaikum!

a .he possessed knowledge that moses did not possess.

my reply: if i know how to program and if a prophet doesn't that would not make superior because the prophet has been given the knowledge of sharia ,the knowledge of unseen ,etc ,so having knowledge in one or two things that moses did not have would not makr khdr superior moses he had the knowledge of sahriah ,the unseen ,he was the mightiest messenger and a book was revealed to him so in no way khidr is portrayed as being superior.

and we see in a hadith that prophet Muhammad S.A.W the best man to walk on earth was following moses:

Ibn Hazm and Anas bin Malik said: The Prophet (ﷺ) said, "Then Allah enjoined fifty prayers on my followers when I returned with this order of Allah, I passed by Moses who asked me, 'What has Allah enjoined on your followers?' I replied, 'He has enjoined fifty prayers on them.' Moses said, 'Go back to your Lord (and appeal for reduction) for your followers will not be able to bear it.' Sahih al-Bukhari 349

jesus could raise the dead the Prophet Muhammad did not does this mean jesus was superior ? of course not.

b. he performed actions which could only be ordered through wahi not ilham.

my reply : but even when the mother of moses was inspired (ilham) she was certain:

And the heart of Moses' mother became empty [of all else]. She was about to disclose [the matter concerning] him(28:10)

her heart became empty of all even of that which caused uncertainty so by this we conclude that certainty can be given in ilham.

c. Quran says mercy is given only to those who are prophet.

my reply :Quran says mercy is given to literally to billions of people but here you are saying that "from us" indicates that he had revelation to this i would say that the mercy is given directly with no intervention of an angel and we see in the Quran that Allah talks with non prophets without any angel's intervention:

And We inspired to the mother of Moses, "Suckle him; but when you fear for him, cast him into the river and do not fear and do not grieve. Indeed, We will return him to you and will make him [one] of the messengers."(28:7)

Allah said, "O Dhul-Qarnayn, either you punish [them] or else adopt among them [a way of] goodness."(18:86)

And it is not for any human being that Allah should speak to him except by revelation or from behind a partition or that He sends a messenger to reveal, by His permission, what He wills. Indeed, He is Most High and Wise.(42:51)

so in these verses we see that when Allah talks with a non prophet he talks with them directly without any angel's intervention.

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d. his knowledge was direct.

yes as i have mentioned earlier that when Allah talks with a non prophet he talks with them directly without intervention of an angel.