In summary:
All scholars of the Quran read the verse of Al-Birr 2:177 as Al-Kitab,
ليسالبرأنتولواوجوهكمقبلالمشرقوالمغربولكنالبرمنآمنباللهواليومالآخروالملائكةوالكتابوالنبيينوآتىالمالعلىحبهذويالقربىواليتامىوالمساكينوابنالسبيلوالسائلينوفيالرقابوأقامالصلاةوآتىالزكاةوالموفونبعهدهمإذاعاهدواوالصابرينفيالبأساءوالضراءوحينالبأسأولئكالذينصدقواوأولئكهمالمتقون
Dr. Kamal Omar translation:
"It is not Al-Birr that you turn your faces to the East and the West; but Al-Birr is this: one who has Believed in Allah and the Last Day, and the angels and Al-Kitab and the Prophets; and he gave his wealth out of His love to close relations, and members of the weaker class and the needy and who has become unpossessed while in travel, and those who are compelled to put up a request; and for giving freedom to one who is in bondage, and he established Salat and he paid off Zakat; and who fulfill their promises and contracts when they have ratified (any); and the patient and perseverant in states of pain and suffering and throughout states of panic — such are the people who have proved (their Belief in Allah) and these are the ones who are Al-Muttaqun"
The only differences here was in recitation: الْبِرُّ , الْبِرَّ , وَلَٰكِنِ الْبِرُّ , وَلَٰكِنَّ الْبِرَّ , وَالنَّبِيئِينَ , وَالنَّبِيِّينَ but the meaning remains the same.
Therefore, part of Al-Birr is to believe in Al-Kitab and not Kutub.
The other verses mentioned were 2:285, 4:136, 66:12 and their variations influence belief of Kitab or Kutub.