I started a while ago and I wonder if the use of opacity is allowed, as well as the use of effects, such as small particles of explosions (following the color palette)
This. There is a participant using the fade effect of the lcd/ simulating ghosting. As long as you use it to try and make your game more accurate to what the Nokia was capable of it should be fine.
Edit: To add onto this jmcm16 did some research and posted it in the discord server.