All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
There is no Hadeeth that implies that one should recite only the verse 255 from Chapter Al-Baqarah in the prayer or outside the prayer.
As regards what is mentioned in regard to reciting it when going to bed and after every obligatory prayer for instance, then the Sunnah is achieved by reciting it and if one recites one verse or two verses or more after it without believing that this addition is a Sunnah, then this is permissible.
Allaah Knows best.