Short answers, pulled from the story.
The Treaty on the Final Settlement with Respect to Germany was signed in Moscow on the 12th of September 1990. This agreement paved the way for German reunification which occurred on the 3rd of October 1990.
The treaty confirmed the internationally recognized border along the Oder Neisse line established after World War II. A separate German Polish Border Treaty signed on the 14th of November 1990 reaffirmed this common border binding under international law.
United Germany became fully sovereign on the 15th of March 1991 upon deposit of the last instrument of ratification. The Four Powers renounced all rights they formerly held regarding Germany including Berlin before this date.
Active personnel decreased further below 183,000 by 2025 while remaining well below the original treaty limit of 370,000 total personnel. The government aims to increase forces moderately up to 260,000 following the 2022 Russian invasion of Ukraine.
No written minutes or recordings exist confirming a promise that NATO would not expand one inch eastward during the conversation on the 9th of February 1990. Mikhail Gorbachev stated in 2014 that assurances pertained only to East Germany and his aide Eduard Shevardnadze agreed the question never came up in talks.