It is not possible to see the Prophet (peace and blessings of Allaah be upon him) (in a dream) in anything but his true form
Question

Is it possible to see the Messenger (peace and blessings of Allaah be upon him) in dreams in several forms, i.e., for one person to see him in one form and for another to see him in another form?.
Praise be to Allah.It should be noted that the Prophet (peace and blessings of Allaah be upon him) said: “Whoever sees me in a dream has indeed seen me, for the Shaytaan cannot imitate me.” Narrated by al-Bukhaari, 6994; Muslim, 2266 – this version narrated by Muslim. 
In their commentary on this hadeeth, the scholars said that this is to be understood as referring to seeing the Prophet (peace and blessings of Allaah be upon him) in the physical form that is described in the saheeh ahaadeeth, for the Shaytaan cannot imitate the form of the Prophet (peace and blessings of Allaah be upon him). 
But if the Shaytaan comes in another form, whether one is asleep or awake, then lies and says, “I am the Messenger of Allaah (peace and blessings of Allaah be upon him),” then this is false and does not count as seeing the Prophet (peace and blessings of Allaah be upon him). 
So you should know the physical attributes of the Prophet (peace and blessings of Allaah be upon him). Please see question no. 1512. These attributes have been mentioned in many ahaadeeth which describe his stature, his hands, his forearms, his mouth and teeth, his eyes and his hair – (peace and blessings of Allaah be upon him). 
There were many people who resembled the Prophet (peace and blessings of Allaah be upon him). Those who most resembled him were al-Hasan ibn ‘Ali (may Allaah be pleased with him), and ‘Abd-Allaah ibn Ja’far ibn Abi Taalib. So if you see the Prophet (peace and blessings of Allaah be upon him) in the form that is narrated in the Sunnah, then you have truly seen him, but if you see him in a form that is other than that described in the Sunnah and the Seerah – such as if you see him clean-shaven, or missing a hand or foot – then there are two scholarly points of view in this case: 
1 – That this is indicative of a person’s shortcoming in religious commitment 
2 – The view that Shaykh al-Islam Ibn Taymiyah thought more likely to be correct, which is that this is a false image that comes from the Shaytaan, especially if one sees it whilst awake. That is definitely a false image, because the Prophet (peace and blessings of Allaah be upon him) is alive in al-Barzakh and no one can see him whilst he is awake and he cannot visit anyone or speak to him. 
What some people claim, that the Prophet (peace and blessings of Allaah be upon him) came to them when they were awake, and spoke to them and told them about things, this undoubtedly comes from the shayaateen (devils) and the jinn, especially since that did not happen to the greatest Sahaabah such as Abu Bakr, ‘Umar, ‘Uthmaan, ‘Ali, al-Zubayr, Talhah, ‘Abd al-Rahmaan ibn ‘Awf, Sa’eed ibn Zayd, Abu ‘Ubaydah and Sa’d, or the people who had been present at Badr or had given their bay’ah (oath of allegiance) beneath the tree, and other great and Allaah-fearing Sahaabah. If anyone claims that he saw the Prophet (peace and blessings of Allaah be upon him) whilst he was awake, then undoubtedly the one who appeared to him was a devil or a jinn, and no ruling can be established from that. Something worse than that happened to Shaykh ‘Abd al-Qaadir al-Jilaani (may Allaah have mercy on him), when he saw someone sitting on a throne between heaven and earth, saying, “I am your Lord.” He said: “Be gone, enemy of Allaah, for you are Iblees.” He said: “How do you know that I am Iblees?” He said: “Because Allaah cannot be seen in this world until we die, and because you said, ‘I am your Lord’ but you did not dare to say, ‘I am Allaah.’” So visions of this sort come from the Shaytaan. We should not be deceived by the stories that are narrated by some people who are thought to be righteous, such as stories about seeing the Prophets and sitting with them. We may believe that they sat with them but with whom were they sitting? They sat with the jinn and devils so that that may cause fitnah (tribulation). But those whom Allaah protects by their following the Qur’aan and Sunnah and reciting dhikrs, Aayat al-Kursiy, al-Mi’wadhaat (the soorahs seeking refuge with Allaah) and seeking the help of Allaah, will be protected against that in sha Allaah, as happened with the awliya’ (close friends of Allaah) and those who fear Him – as was narrated by Shaykh al-Islam in his valuable book: al-Furqaan bayna Awliya’ al-Rahmaan wa Awliya’ al-Shaytaan. 
There remains another issue to which we must refer, which is that if a person sees the Messenger of Allaah (peace and blessings of Allaah be upon him) in the form described in the saheeh Sunnah, this is glad tidings, telling him that he will also see him when he is awake. If he tells him of some shar’i matter that seems to go against the apparent meaning of the Qur’aan and Sunnah, should he follow what he has been told or follow the apparent meaning of the Qur’aan and Sunnah? Or if he tells him about some matter concerning which there has to be proof – such as the people being shown the new moon when they did not see it, and he says that tomorrow is Ramadaan – should he follow that or not? Or if he tells him that So and so stole something from So and so, or that in the case of a dispute So and so is in the right – should he bear witness to that? 
The scholars have stated that if a person sees the Prophet (peace and blessings of Allaah be upon him) and he tells him something that goes against the apparent meaning of the Qur’aan or Sunnah, or tells him of some matter concerning which there has to be proof, he should not act upon it, because what one sees in a dream is not binding; what is binding is the facts that one learns when awake. You should note that the dreams of the Prophets are wahy (revelation), but seeing the Prophets in a dream is not wahy – according to scholarly consensus. Rather it is bushra (glad tidings), as was explained by al-Nawawi (may Allaah have mercy on him).