I can write more details via DM, I did lots of this stuff with kids to adults for popularisation. :)

Many cool things. There is cool stuff with flower beads (you can get them in any flower shop). youtu.be/o0hCcN6C8r8?...

Matching the index of refraction, glass bowl + beads.

Diffraction - take an old CD + mirror. Reflection of CD colors you see on CD are different then in mirror.