Mi FAQ personal sobre el idioma inglés, para no tener que buscar siempre lo mismo.
in/on refer to location/position. Into/onto refer to movement. Hence:
Put the book into the box. The book is in the box. Put the box onto the table. The box is on the table.
'Upon' is a poetic alternative to 'on'. You can wish upon a star / rainbow, or more prosaically wish on a star / rainbow. (In fact I am not sure that we do wish on / upon stars or rainbows in the UK, but I have heard of doing so from American usage). I am not sure in what context one might say 'there on the rainbow'. What exists on a rainbow?
'Unto' is an archaic alternative to 'to'.