Yes, the Ukrainian government switched it's public stance on...

Yes, the Ukrainian government switched it's public stance on NATO on a few occasions. But in the background, documents and agreements were being signed, that paved a way towards Ukraine's closer co-operation with NATO (a military bloc).

All the Russian guarantees of Ukrainian sovereignty and territorial integrity were based on Ukrainian Declaration of Sovereignty.

Wikipedia:

Ukraine joined NATO's Partnership for Peace in 1994 and the NATO-Ukraine Commission in 1997, then agreed the NATO-Ukraine Action Plan in 2002 and entered into NATO's Intensified Dialogue program in 2005. In 2010, during the premiership of Viktor Yanukovych, the Ukrainian parliament voted to abandon the goal of NATO membership and re-affirm Ukraine's neutral status, while continuing its co-operation with NATO.

It's Ukraine that failed to fulfil it's aspirations of non-neutrality, which were stated in the Declaration of State Sovereignty.