I knew that:

• yet should be used in negative sentences and questions.
• still should be used in affirmative sentences.
• We can use yet in affirmative sentences containing this pattern:have yet to

However, I was reading a passage and came across with this sentence:

So much sentimentality is attached to the rose in popular culture that it is difficult to separate the original mythological and folkloric beliefs from the emotional excess that surrounds the flower. Yet if we look into the beliefs, we find that the rose is much more than the mere symbol of romantic love invoked by every minor poet and painter.

1. Is it grammatical to use "yet" or we should use "still"?

2. What would be the difference if one put "still" there?

I knew that:

• yet should be used in negative sentences and questions.
• still should be used in affirmative sentences.
• We can use yet in affirmative sentences containing this pattern:have yet to

However, I was reading a passage and came across with this sentence:

So much sentimentality is attached to the rose in popular culture that it is difficult to separate the original mythological and folkloric beliefs from the emotional excess that surrounds the flower. Yet if we look into the beliefs, we find that the rose is much more than the mere symbol of romantic love invoked by every minor poet and painter.

the author continues to enumerate several different meanings or 

connotations of the "rose" in different cultures. 

1. Is it grammatical to use "yet" or we should use "still"?

2. What would be the difference if one put "still" there?