Regarding: 'And We granted the vision (Ascension to the Heaven "Miraj") which We showed you (O Muhammad as an actual eye witness) but as a trial for mankind.' (17.60) It was an actual eyewitness which was shown to Messenger of Allah ﷺ during the night he was taken on a journey (through the heavens). And the cursed tree is the tree of Az-Zaqqum (a bitter pungent tree which grows at the bottom of Hell).
هِيَ رُؤْيَا عَيْنٍ أُرِيَهَا رَسُولُ اللَّهِ ﷺ لَيْلَةَ أُسْرِيَ بِهِ {وَالشَّجَرَةَ الْمَلْعُونَةَ} شَجَرَةُ الزَّقُّومِ