While there may have been VERBAL discussions of Ukraine remaining un-aligned, that was NOT part of any document signed by anyone.
The Act of Declaration of Independence of Ukraine does state that the territory of Ukraine is indivisible and inviolable. [1] Their constitution of 1996 says the same thing. [2] There are updated constittutions in 2004 and 2010, [3] though I don't know the exact details of changes.[4]
[1]
https://en.wikisource.org/wiki/Act_of_Declaration_of_Independence_of_Ukraine
[2]
https://en.wikisource.org/wiki/Constitution_of_Ukraine,_1996
[3]