The first post-Soviet Russian attempt to breach the territorial integrity of sovereign Ukraine and annex Ukrainian territories happened in 2003 (not a typo), which was not even a decade after the signing of the Budapest Agreements. It also happened before the famous eastward expansion of the NATO.
In 2003, the Ukrainian president was on a state visit to Latin America, which is very far away. Russians used that moment to proceed with a far-reaching and long-existing plan to move towards annexing the Crimea. The first step in the plan was the Tuzla Island. It’s a tiny strip of land between mainland Russian and the Crimea. While the Ukrainian president was in a different hemisphere, Russians (who, once again, only a few years ago recognized and guaranteed Ukraine’s territorial integrity) decided that Tuzla was Russian land and started building a dirt road towards it. Which makes it extremely easy to then build a stretch of road to the Crimea.
The Ukrainian President immediately returned and pushed back. Russians had to wait until 2015 to build their dirt road and until 2018 to annex Tuzla.
There is no evidence to support the idea that Russia at any time was going to keep its promise to respect Ukraine’s sovereignty. Or Belarusian sovereignty. Russia did everything to compromise Belarusian nation-building in the 1990s (and, of course, since then). This was also before the NATO eastward expansion.