Peace Mubashir,
ANSWER TO QUESTION 1:The concept of answerability and judgement is well attested in the Bible (Both OT and NT).
Ezekiel 44:12 (KJB)"Because they ministered unto them before their idols, and caused the house of Israel to fall into iniquity; therefore have I lifted up mine hand against them, saith the Lord GOD, and they shall bear their iniquity"Matthew 25:46 (KJB)"And these shall go away into everlasting punishment: but the righteous into life eternal"ANSWER TO QUESTION 2:'Suhuf' are written pieces of paper / parchments or of a skin and something collected between two boards. It is usually better rendered as scrolls.
The Quran speaks of the existence of the 'suhuf' of Prophet Abraham without giving any indication as to when they existed. What is interesting to note is that the Quran does not speak about its possible alteration at the hands of previous followers of scriptures. Nor does it mention any human accretions as it does with the case of the Torah and Bible.
This leads me to consider the possibility that the 'Suhuf' of Abraham was (a) not an extant text even at the time of the Prophet or (b) That it was a scripture that existed but was regarded as non canon (Apocrypha - such as the Testament of Abraham) by both the Jews and Christians followers. However, there is every likelihood based on its mention in the Quran along with the suhuf of Prophet Moses, (87:19), that it was an extant literature at the time of the Prophet but later became lost or faded from memory.
Some scholars have surmised that this 'Suhuf' could be a reference to certain literature such as the Sefer Yetzirah (Book of Formation) or other non-canonical works as the Testament of Abraham mentioned above.
ANSWER TO QUESTION 3:With regards the Injeel, it has never been described by the Quran as a 'kitab' or 'suhuf'. In fact, a couple of times it is not even recognised as 'scripture' in the same sense as the Torah or Quran (Possibly a reference to major law bearing scriptures).
046:012"And before this (Arabic: wamin qablihi), was the Book (kitab) of Moses as a guide and a mercy: And this Book (kitab) confirms (it) in the Arabic tongue; to warn those that do wrong and as glad tidings to those who do right" The above verse seems to negate that there was a 'kitab' before the Quran other than the Torah.
This is also confirmed in 11:17 and in 46.30 where the Jinn also seem to have heard the Quran as a 'dialog in truth' but after the one given to Prophet Moses.
It can be argued from the Quran that the Injeel comprises the 'teachings' and 'wisdom' imparted by Prophet Jesus. This was then later communicated by Prophet Jesus's disciples to later compilers on their behalf.
However, it is important to note that whatever the 'nature' of the injeel, the Quran confirms (musaddiqan) whatever essence of the Christian writings was extant at the time of revelation of the Quran. This does not seem to imply that the Injeel that was in the possession of the Christians at the time of the Prophet was corrupted beyond recognition as is sometimes asserted by Muslims.
003:003-4"He revealed to you the Book in truth confirming that which is between his hands (Arabic: ma bayna yadayhi) (i.e. authenticating what is present with it of the Torah and Bible) and He revealed the Torah and the Gospel before this as a guidance for mankind; and He revealed the criterion. Indeed, those who disbelieve in the verses of God, for them is a severe punishment and God Almighty is all able to retribute"Please note the relationship of the scriptures. The Quran confirms the inherent veracity of the previous scriptures that was existing at the time of revelation while leaving itself as the criterion to judge right from wrong (furqan).
Prophet Jesus clearly had inspired wisdom from a young age and he taught this wisdom confirming the Torah that was with him. It seems likely to me that these teachings were later communicated and compiled and became known as the Injeel (Gospels).
Please see the following related article:
'BETWEEN HIS HANDS' OR 'BEFORE IT' (MA BAYNA YADAYHI)http://www.quransmessage.com/articles/between%20hands%20or%20before%20it%20FM3.htmI hope this helps.
Joseph.