When Rio creates the flower in her palm, in the next shot, her hand is facing down.
As the coven sings their rendition of 'The Witches Road', Lillia starts out playing a set of miniature cymbals ("zills," as she explains that she has been taught to play) that transform into a triangle halfway through the song without explanation. They then transform into a pair of maracas, showing that the song itself is magickal and is helping the coven fight the curse.
The previous episode ended with Agatha and the gang clearly not knowing who Sharon is. However, this episode begins with her burial on the road & everyone knows who she is and what happened.
This is incorrect. Agatha always called Sharon Mrs Hart, the id given to her by Wanda, despite being told her real name is Sharon. This was to show Agatha's dismissive attitude towards others.
When the coven is discussing why Mrs. Hart is died, possible reasons are that Alice Wu didn't protect her and that Jennifer Kale only gave Sharon Davis one dose of the potion when Sharon Davis had two glasses of poison. Nobody present realized Sharon Davis' hair didn't make it in to the potion, and so the potion might not have worked on her.