pouët.net

It's one of the mainstream-ish but softer ones, every second DOS-kiddy had it somewhere on floppy beside other demos and a copy of Body Blow and Epic Pinball I think... like me /o\. My guess was it's a demo from TBL but an unlucky search for it means I could miss it with greetings to TBL or I was starting some TBL-demos too often. So, this should be easy for you more name oriented fellowers than for me:
a dark flower (rose?) rise up with a dark spacy background and some lyric in white font says: "this is for you my friend"...
1st time I run it I got infected completely and started to be 'offline'. ^^ ty

hmm, maybe this could help... ;-)

Doesn't tell me anything but because I am thinking of 1993 and TBL weren't even at the time (unless on the Amiga).

TBL do have flowers and 3d spherical coordinate flower like thingies but nowhere I remember "this is for you my friend" in any of their lyrics.

FR-43 time Index comes to my mind, it includes said lyrics and flowers, but it's 10 years later

Did you check the MindCandy Volume 1: PC Demos already?

RufUsul: bookmarked for a later search
v3nom: The atmosphere and style in 'time index' is the right direction.
Dresdenboy: I did a more, then less backflashing thumbnail-preview through Mind Candy Vol 1. - No, or I missed it.

I believe it wasn't from TBL anyway. It started almost black and began to be detailed slowly, for about like 50 seconds. (as far I can remember)

your first description made me think of replay - some bookprint and a broken heart but it doesnt match the color scheme nor 90s timeframe you describe. also in a similar style 3state - sonnet is too newskool, so. no idea and thus it's probably not as mainstream as you think ;)

Might not be, but https://www.pouet.net/prod.php?which=287 would start a bit dark, has flower, lyrics. Can't find the exact phrase "this is for you my friend" though.

not for real. thank you anyway

Please post the demo here whenever you find it.