Russian Tsarevnas Abroad

This is sort of a double question - but each question can be considered separately (I'm just too tired to bother with creating multiple threads, since they all deal with basically the same topic).

1. Boris Godunov planned to marry his daughter, Xenia Borisovna (1582-1622) to two Scandinavian princes in 1600 and 1602 respectively.
1.1. The first engagement, to Gustav Eriksen Vasa, was eventually broken because of the fact that Gustav paraded his mistress around as though she were the tsarina herself.
1.2. The second was to Duke Johan of Schleswig-Holstein, the youngest son of King Frederik II of Denmark. But much like the later Elizabeth Petrovna's two proposed grooms (a prince of Holstein and a prince of Hesse-Homburg) he died before the wedding could take place.

2. In 1640, Irina Mikhailovna, daughter of Tsar Mikhail Romanov and sister of Tsar Alexei, was engaged to Valdemar Christian (prince?) of Holstein, son of Christian IV of Denmark and Kristin Munck. However, it brought the added condition that he convert to Orthodoxy in order for the wedding to take place. Valdemar refused and was thrown in a Russian jail until 1645.
IIRC there was the rumor that Mikhail loved his daughter too much to marry her off, and imposed the conversion to Orthodoxy sort of as a way to stall/refuse the marriage without Russia losing face.

What if any of these marriages had taken place?
 
Second case was not marrying off, but rather creating a husband Russian feudal prince and inserting him into succession line - hence why bastard son was considered, who could be converted without any fuss. And hence why conversion was mandatory condition.
But "a principality in barbaric country was not worth a mass", apparently.

Case 1.2 is most funny as Holstein dynasty might get to rule Russia a century earlier than OTL, and Xenia was to leave abroad (and not husband to move in Russia and created a prince unlike case 2).
 
It may seem a little stupid to ask this question, but if Xenia Godunova marries into the house of Holstein, would Denmark react to Feodor II's deposition with anything more than perhaps a strongly worded letter? Or would it be outright war?

And if she marries Gustaf Eriksen of Sweden, would Russia get involved in a war with Sweden to put Gustaf on the throne? Or would they simply content themselves with him being a landless prince married to a tsarevna (not a bad prospect if Xenia becomes Tsarina suo jure (can she?)). I can't remember when he was given the principality of Uglich (before or after the engagement), but IIRC he spent his last years in abject poverty.
 
And if she marries Gustaf Eriksen of Sweden, would Russia get involved in a war with Sweden to put Gustaf on the throne? Or would they simply content themselves with him being a landless prince married to a tsarevna (not a bad prospect if Xenia becomes Tsarina suo jure (can she?)). I can't remember when he was given the principality of Uglich (before or after the engagement), but IIRC he spent his last years in abject poverty.
Yeah definitely. OTL they decided to get involved when their only excuse was "look! Its (another) prince dimitri!" so i dont see why they wouldnt if they had an actual claim.

Denmark during this time period fought in the 30 years war and a separate short war with Sweden, so their might be a possibility of a Danish punitive expeditions against Poland/Sweden/Russia in regards to case 1.1
 
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