My best guess is very similar to you fourth scenario.
I think, that one of the main Putin’s goal (maybe his very terminal goal, but I’m not sure) is to solve the Ukrainian problem, and then quit the game as a triumphant (after president’s election at 2024; but he has option to continue work on it until 2030, if he choose so and nothing changes significantly). Putin’s time is relatively short—he is 69 years old, and there are some rumors (not very reliable, thought) that he is somehow sick. So achieving his main goal in two years is very preferably to him, but there are still another six president’s years, if he need it and can afford it.
Ukraine is one of few ex-USSR republics that is not loyal to Putin’s government, and he obviously perceive that as a big problem. So the main Putin’s current goal, as far as I can assume, is to create artificial loyal states (on the basis of pretending to independence Donetsk Oblast and Luhansk Oblast of Ukraine) between Russia and NATO. There are already couple of such states with limited recognition around Russia (Abkhazia and South Ossetia, both of which are commonly recognized as parts of Georgia), so it is appropriate way for Putin to create a buffer zone.
Installing a puppet government at the Ukraine, as far as I can see, is the secondary goal, but also desired.
Speaking of price of the invasion in terms of Russian economics, there is Russian National Wealth Fund, which continuously grew up during almost all COVID pandemic. There were thoughts earlier, that this NWF was intended for possible war (especially considering, that pandemic was not reason to spend it). Today I say news, that government is planning to spend it to support the economics (personally, I consider it as a relatively good sign—if they started to spend the stock for a rainy day then they currently do not plan to escalate current situation even further).
My best guess is very similar to you fourth scenario.
I think, that one of the main Putin’s goal (maybe his very terminal goal, but I’m not sure) is to solve the Ukrainian problem, and then quit the game as a triumphant (after president’s election at 2024; but he has option to continue work on it until 2030, if he choose so and nothing changes significantly). Putin’s time is relatively short—he is 69 years old, and there are some rumors (not very reliable, thought) that he is somehow sick. So achieving his main goal in two years is very preferably to him, but there are still another six president’s years, if he need it and can afford it.
Ukraine is one of few ex-USSR republics that is not loyal to Putin’s government, and he obviously perceive that as a big problem. So the main Putin’s current goal, as far as I can assume, is to create artificial loyal states (on the basis of pretending to independence Donetsk Oblast and Luhansk Oblast of Ukraine) between Russia and NATO. There are already couple of such states with limited recognition around Russia (Abkhazia and South Ossetia, both of which are commonly recognized as parts of Georgia), so it is appropriate way for Putin to create a buffer zone.
Installing a puppet government at the Ukraine, as far as I can see, is the secondary goal, but also desired.
Speaking of price of the invasion in terms of Russian economics, there is Russian National Wealth Fund, which continuously grew up during almost all COVID pandemic. There were thoughts earlier, that this NWF was intended for possible war (especially considering, that pandemic was not reason to spend it). Today I say news, that government is planning to spend it to support the economics (personally, I consider it as a relatively good sign—if they started to spend the stock for a rainy day then they currently do not plan to escalate current situation even further).