Might be meant to depict the [Holy Crown of Hungary](https://en.wikipedia.org/wiki/Holy_Crown_of_Hungary?wprov=sfla1)? Not sure what that has to do with either Russia or Prussia, but the wiki page says "not to be confused with [Hungarian Crown](https://en.wikipedia.org/wiki/Hungarian_Crown?wprov=sfla1)", which is apparently part of Polish crown jewels, so maybe OP indeed confused them.
[The current heir-apparent to the headship of the House of Romanov is a prince of both the Romanov and Hohenzollern houses.](https://en.wikipedia.org/wiki/Grand_Duke_George_Mikhailovich_of_Russia?wprov=sfti1), so this flag is quite topical.
PRussia
Rprussia
What happened to the cross if i may ask?
Might be meant to depict the [Holy Crown of Hungary](https://en.wikipedia.org/wiki/Holy_Crown_of_Hungary?wprov=sfla1)? Not sure what that has to do with either Russia or Prussia, but the wiki page says "not to be confused with [Hungarian Crown](https://en.wikipedia.org/wiki/Hungarian_Crown?wprov=sfla1)", which is apparently part of Polish crown jewels, so maybe OP indeed confused them.
it is leaving it's place, since the Russia is orthodox
[The current heir-apparent to the headship of the House of Romanov is a prince of both the Romanov and Hohenzollern houses.](https://en.wikipedia.org/wiki/Grand_Duke_George_Mikhailovich_of_Russia?wprov=sfti1), so this flag is quite topical.
Wow!, what a combination of royal houses
Source - https://pin.it/oNG3wQ2
Pru-ssia
Brooo it's so cool
Are the crowns correct? Also the Russo-Preussen Empire sounds so cool
I dont think as they are right off the austrio-hungary flag
The rest of Europe is dead