Your first paragraph is best ignored. It is a Gish gallop of RetCon (i.e. historical revisionism). It would take an entire page to respond in full. Since you didn't actually make any statements but instead asked leading questions, I'll respond as such: No. Yes. Which neighbor?

The highlighted text refers to the Budapest Memorandum that ALSO stated that the signees would refrain from meddling in each other elections. The US broke this in 2004 and then continued through to openly supporting the coup in 2014. Why should Russia continue to follow an agreement that the US had already broken?

Regarding nukes, they were not Ukraine's. They were Russia's, and only Russia had the codes to use them. There was no question about that. The issue was, with Russia being stripped of natural resources and state company money, the State was very poor and the West was (correctly) concerned whether Russia could safely maintain the nukes.

There is more than one definition of "fortifications" and the issue was not "dragon's teeth" at the border. It is missile flight time from Ukraine to Moscow, and the flat plains between Ukraine and Russia that had been used in the last great war to destroy an area of Russia equivalent to the area of the US east of the Mississippi.

Your argument about who attacked whom is again facile. Of course Russia was wrong to attack Ukraine. Ukraine was also wrong to spend 8 years shelling the ethnic Russians in the Donbas. Ukraine had lined up 60,000 troops on the border to the Donbas in early Feb 2023, and had doubled its shelling in preparation to finally invade in force and wipe out the ethnic Russian separatists.

The UN charter does make an exception to invasions being illegal - when that invasion is done to prevent an even worse crime. That is what Russia is claiming. Again, I'm not an international lawyer, so that would need to be adjudicated.

Please point out a conflation I made.