Is it possible to paste notes from FL studio's piano roll into reaper when using fl as a vst in reaper?

I think it is not possible. I don't have FL, but I am pretty sure there is an option to export MIDI and then import it in Reaper. Not sure if it is possible when using FL as a plugin.

I am not sure, but I don't think it is possible. But you can export MIDI from FL and import it into Reaper.

definitely not. FLs per midi piano roll save works with fruity score files, not regular midi. in order to bring midi from FL to reaper, you have to go into pattern mode, make sure the "leave end" or whatever option is off, and then export it as a midi, then bring it into reaper.

You can also go directly into the pattern and the one you got some notes on...go inside the pianoroll-> pianoroll options-> file-> export as midi. This is useful if you only want to have midis from ex a bassline, kick etc. In song (if you want to save the whole midi of the song) mode you need to go : File-> export-> midi file-> create a name and save-> make sure this loop reminder is in "leave reminder" mode . If you have a multi vsti and have for ex 4 different midinotes (multimidi) (channel 1,2,3 etc) in the same pianoroll i think this works also to save...not sure though..