Why not " to rika vsichni". I guess I'm having trouble with where to use kazdy and where to use vsechno.
každý is singular, literally it means every - každý člověk = every person
všichni is plural, literally it means all, everyone - all (the) people = všichni lidé
"To říkají všichni." is possible
Does "každý to říká!" mean the same?
Yes, it does. One would likely stress word "každý" in pronunciation of both sentences.
Traditionally, the version "To každý říká!" won't be accepted.
That is quite strange. I found just one similar example in the Czech national corpus: "TOMÁŠ VERNER je talentem, to každý říká."
Not sure if it should be accepted.
It means that the stress is on "říká" ("nepíše, "nespívá" ale říká)? Or it depends also on the intonation?
Who knows how did they pronounce it, it is from a newspaper. But I would expect a rising intonation on "říká". But it is very hard to describe it. I would better avoid discussing the stress in this case.
Alright. Thank you!