Russia would be very happy to install a puppet regime in Ukraine, as long as they had some certainty this regime would be stable and subservient to their interests. We know for a fact that they don't care about necessarily invading other countries as long as those countries are subservient: they are not planning to annex Belarus, nor did they have any real problems with Ukraine as long as it was led by their preferred leaders and it was not making any overtures to NATO or the EU.
The exact same thing will happen in Venezuela: the USA will be happy with any leader that they have confidence will represent US interests, stop doing any business with Russia or Iran, and that they think will last. If instead another member of Maduro's party looks likely to win power, either now or in the near future, they will certainly not allow that to happen, even if it were to happen as a result of free elections.
Yes, they did, and there was no attempt to annex Ukraine before that regime fell, I said as much in my comment.
Note that this is not in any way an attempt to justify Russia's actions, quite the contrary. I'm using the comparison to Russia's obviously horrible actions in Ukraine to condemn the USA's equally horrible actions in Venezuela.
In the 90s, the status of Crimea was an internal dispute in the newly-formed Ukrainian state. The status of Crimea as a part of the new Ukrainian state at this time was not yet settled in any way. The territory only became firmly a part of Ukraine in 1995.
The 2003 dispute over the island of Tuzla - whose status had not been clearly settled during the independence of Ukraine from the USSR - was settled diplomatically. If you call this occasion an "attempt to annex Ukraine", then we could equally say that "Romania attempted to annex Ukraine" when the countries had several rounds of negotiation and arbitration for control of Snake Island in the Black Sea.
The only reason Russia has been reluctant to formally annex territories it broke away from other countries until 2022 was minimizing economic damage to itself. They knew how sensitive the western countries were to forceful changes of the world map, and felt no need to inflict economic sanctions on themselves for a mere symbolic act of annexing a territory they already fully controlled.
Once that Rubicon was crossed (sanctions were in place and there was nothing to lose), they annexed the four regions of Ukraine that they partially controlled.
The exact same thing will happen in Venezuela: the USA will be happy with any leader that they have confidence will represent US interests, stop doing any business with Russia or Iran, and that they think will last. If instead another member of Maduro's party looks likely to win power, either now or in the near future, they will certainly not allow that to happen, even if it were to happen as a result of free elections.