What is the ruling on pausing at the word "al-muttaqeen" (the pious) in the verse: "That is the Book about which there is no doubt, a guidance for the pious"? And is it a necessary or permissible stop? And if it is permissible, which is more preferable: continuing or stopping?

Stopping in the Holy Quran is not obligatory unless it suggests a meaning that contradicts the intended one. The conventions for stopping are based on scholarly interpretation and there is disagreement among scholars regarding them. As for the mentioned verse in Surat Al-Baqarah, some Qur'anic manuscripts place the permissible stop sign at (no doubt therein), while others place the embrace-stop sign at both locations. It is recommended to stop at (no doubt therein), even though stopping at the other location is more preferable.