5 Vertical pink lines - Imac 2011 - Won't boot up
Safe mode and recovery mode tend to not load specific graphic drivers or acceleration, so the clear signal there tends to reinforce the hardware trace and LCD are still fine and the visual artifacts are GPU failures.
Your research is likely right that reflowing the solder might help remedy this or it will point to a more embedded failure. Either way, kudos for trying to reuse this. Next would be repair or recycle or sell for parts. People will want the power supply and lcd and other parts.