The Russian invasion is Ukraine is likely to result in Russia being unable to supply gas to Europe, as Europe will be unwilling to buy Russian gas over the long term.
It won't change much for Russia. When there's a seller, there's always a buyer. If not at this price, there will be at a lower one. Some countries will buy Russian Gas.
Eh, not necessarily. Iran and Venezuela both have difficulty selling their oil as both are heavily sanctioned by the US.
The problem currently is that Western countries heavily depend on Russian oil for their energy needs. If Europe can start importing natural gas from the US and elsewhere, it can boycott Russian energy.