The presence or absence of hydroxyl group on which carbon atom of sugar differentiates RNA and DNA ?

The outer electron configuration of $$Gd$$ (Atomic No. $$64$$) is :

Sodium ethoxide has reacted with ethanoyl chloride. The compound that is produced in the above reaction is

Phenol is heated with a solution of mixture of KBr and KBrO₃. The major product obtained in the above reaction is