His aim is to rebuild the extension of the old USSR and that includes the Baltics, the Balcans, Poland, half of Germany, Slovakia, ... One bit at a time, by subversion or invasion don't matter.
So according to you he'd like to build a new USSR, because the countries you've mentioned (apart from the Baltics) were never a part of the Soviet Union, but Ukraine was!
Putin treats the former Soviet Union countries like they're a part of Russia, which is why he attacked Chechenya, but he knows Poland, Germany and Slovakia are ethnically different and would never submit.
Also, if we're talking about the former Warsaw Pact, why mention Poland and Slovakia, but not Hungary or Czech Republic? They were held exactly the same status in the Soviet Union -as allies.
Unfortunately that's long gone and they have allied themselves with the West.
Even if there was no NATO, Russia would not have enough firepower to conquer these countries. They'd get spread thin transporting troops and vehicles 2000 km into enemy territory and eventually cut off and they know it.
That is, Russia will be the guarantor of security in Europe and ensure stability in the region.
Russian word means nothing. The way they handled The Budapest Memorandum is the latest example of why nobody should ever trust Russia.
To remind you:
The memoranda,(...) prohibited Russia, the United States and the United Kingdom from threatening or using military force or economic coercion against Ukraine, Belarus, and Kazakhstan. I accept the correction. Those countries were not USSR, but they were Warsaw Pact, so clearly under the foot. You just need to remember the Soviet tanks in Prage.