يَا أَيُّهَا النَّبِيُّ (O Prophet!): Allah (swt) addresses all the Prophets by their names, such as:

وَقُلْنَا يَا آدَمُ اسْكُنْ أَنتَ وَزَوْجُكَ الْجَنَّةَ

(And We said, “O Adam, dwell, you and your wife, in Paradise) (Al-Baqara: 35)

 يَا إِبْرَاهِيمُ أَعْرِضْ عَنْ هَٰذَا

(Oh Ibrahim, turn away from this…) (Hud: 76)

يَا نُوحُ إِنَّهُ لَيْسَ مِنْ أَهْلِكَ

(Oh Nuh, he is not of your family…) (Hud: 46)

 يَا مُوسَىٰ إِنِّي اصْطَفَيْتُكَ عَلَى النَّاسِ

(Oh Musa, indeed I have chosen you over the people) (Al-A’raaf: 144)

All the Prophets are addressed by their names except for the Prophet Muhammad (saws), who is addressed as:

 يَا أَيُّهَا الرَّسُولُ بَلِّغْ مَا أُنزِلَ إِلَيْكَ مِن رَّبِّكَ

(Oh Messenger, convey what has been revealed to you from your Lord) (Al-Maidah: 67)

 يَا أَيُّهَا النَّبِيُّ إِنَّا أَرْسَلْنَاكَ شَاهِدًا وَمُبَشِّرًا وَنَذِيرًا

(Oh Prophet, indeed We have sent you as a witness, a bringer of good tidings, and a warner) (Al-Ahzab: 45)

And as in this verse: “Oh Prophet, sufficient for you is Allah,” In these addresses, there is a special status for the Prophet (saws); he is the final Messenger to all of humanity, that is why Allah (swt), honored him with such addresses.

When Allah says: (Oh Messenger), it pertains to matters related to the Message and revelation. When He (swt) says: (Oh Prophet),  it pertains to matters related to ethical conduct.

حَسْبُكَ اللَّهُ وَمَنِ اتَّبَعَكَ مِنَ الْمُؤْمِنِينَ(Allah is Sufficient for you, and for those who follow you among the believers.): That is, Allah (swt) is sufficient for you, and He is sufficient for those who follow you among the believers, this is one interpretation. Another interpretation is that Allah (swt) does not need means to bring victory to you, but it is incumbent upon you to take the necessary measures. In this context, it refers to the strength of the believers who are with him. Both interpretations are valid, and Allah knows best.