Salamun alaikum Brother Mubashir ,
Brother , I do not find any reason why 2:62 is referring specifically to pre-quranic era ONLY.
2:62 (Yusuf Ali)
Those who believe (in the Qur'an), and those who follow the Jewish (scriptures), and the Christians and the Sabians,- any who believe in God and the Last Day, and work righteousness, shall have their reward with their Lord; on them shall be no fear, nor shall they grieve.
2:62 (Shakir) Surely
those who believe, and those who are Jews, and the Christians, and the Sabians, whoever believes in Allah and the Last day and does good, they shall have their reward from their Lord, and there is no fear for them, nor shall they grieve.
2:62 (Pickthall) Lo!
Those who believe (in that which is revealed unto thee, Muhammad), and those who are Jews, and Christians, and Sabaeans - whoever believeth in Allah and the Last Day and doeth right - surely their reward is with their Lord, and there shall no fear come upon them neither shall they grieve.
In corpus.quran , it is translated as
'Those who believed' which can be used while referring to past as well as present situation according to me.
'
Those who believed' is referring to peoples who were Muslims , who reverted to Islam(Submission to Allah) before this verse (2:62) was revealed. (Muslims during time of Muhammad and past times)
28:51 And We have delivered the message, perhaps they may take heed.
28:52 Those to whom We had given the Book before this, they will believe in it.
28:53 And if it is recited to them, they say: “We believe in it. It is the truth from our Lord. Indeed,
we had submitted before it (Arabic - Muslimina)__________________________________________________________________________________________________
Now what you extract from 3:85 depends on
how you translate ISLAM and DEEN as.
'A Religion of Islam' (Islam being untranslated) or 'SYSTEM of SUBMISSION' to Allah.
Please see these articles ,
http://www.quransmessage.com/articles/muslim%20mumin%20FM3.htmhttp://www.quransmessage.com/articles/people%20of%20the%20book%20FM3.htm3:113-114
"
Not all of them are alike: Of the People of the Book are a portion that stand:
They rehearse the verses of God all night long, and they prostrate themselves in adoration. They believe in God and the Last Day;
they enjoin what is right, and forbid what is wrong; and they
hasten in good deeds:
They are in the ranks of the righteous"