A raa (ر) with a Fathah (َ) or Dammah (ُ) on it should be pronounced with a full mouth
A raa (ر) with a Kasrah (ِ) should be pronounced with an empty mouth.
If a Fathah (َ) or Dammah (ُ) appears before a Raa Saakin (رْ), the Raa Saakin will be pronounced with a full mouth
If a Kasrah (ِ) appears before a Raa Saakin (رْ), the Raa Saakin will be read with an empty mouth.
If a Shaddah (ّ) appears on the letter Raa (ر) and has either a Fathah (َ) or Dammah (ُ) it will be pronounced with a full mouth.
لَّيْسَ ٱلْبِرَّ أَن تُوَلُّوا۟ وُجُوهَكُمْ قِبَلَ ٱلْمَشْرِقِ وَٱلْمَغْرِبِ وَلَٰكِنَّ ٱلْبِرَّ
If a Shaddah (ّ) appears on the letter Raa (ر) and has a Kasrah (ِ), it will be pronounced with an empty mouth.
When a Yaa Saakin (يْ) appears before a Raa Mouquf and the letter preceding the Yaa Saakin has a Kasrah (ِ), then the Raa (ر) will be recited with an empty mouth.
When a letter other than a Yaa Saakin (يْ) appears before a Raa Mauquf, and the letter has a Sukoon ( ْ) on it and the letter preceding it has either a Fathah (َ) or Dammah (ُ) on it, then the Raa (ر) will be recited with a full mouth.
