I honestly do not have the time, but I will sacrificially make the time to answer this one:
(10) Can you explain why he says, "Though we have known Jesus in the flesh, we no longer know Him this way," when John warns us about spirits that deny Jesus Christ come in the flesh?
Yes, as a matter of fact, I can accurately explain it.
Here is what Paul said, in context:
2 Corinthians 5:12-16
"For we commend not ourselves again unto you, but give you occasion to glory on our behalf,
that ye may have somewhat to answer them which glory in appearance, and not in heart. For whether we be beside ourselves, it is to God: or whether we be sober, it is for your cause. For the love of Christ constraineth us; because we thus judge, that if one died for all, then were all dead: And that he died for all, that they which live should not henceforth live unto themselves, but unto him which died for them, and rose again. Wherefore henceforth know we no man
after the flesh: yea, though we have known Christ
after the flesh, yet now henceforth know we him no more."
In context, which is always of utmost importance, Paul's stated objective in what he was about to say was to equip his Corinthians hearers with "somewhat to answer them which glory in appearance, and not in heart."
Well, who are these people?
You need to understand the timeframe during which Paul was writing. The people had been under the Mosaic law or the old covenant for approximately 1500 years, and this was a time of great transition from the old covenant to the new covenant which had been foretold of. Under the old covenant, there was a circumcision in the foreskin of one's flesh, and under the new covenant, we need to have a circumcision in the heart or spirit. With such being the case, Paul constantly wrote of a conflict between the flesh and spirit, and although multitudes of professing Christians have been duped into believing that Paul was talking about some alleged dual nature that Christians have, this is not what Paul was speaking about at all. In other words, Paul consistently used certain different words interchangeably to describe life under the old covenant, and some of those words are "law," "flesh (as in an outward fleshly circumcision)," "bondage (because the law left one in bondage to sin)," and "works."
Here, when Paul spoke about "after the flesh," he was alluding not only to those "which glory in appearance, and not in heart," or to those who trusted in the law with its accompanying fleshly circumcision, but he was also referring to how people knew Christ "after the flesh," or to how they recognized him under the old covenant.
This same Paul, in this same epistle, went on to say this:
2 Corinthians 11:12-23
"But what I do, that I will do,
that I may cut off occasion from them which desire occasion; that wherein they glory, they may be found even as we. For such are false apostles, deceitful workers, transforming themselves into the apostles of Christ. And no marvel; for Satan himself is transformed into an angel of light. Therefore it is no great thing if his ministers also be transformed as the ministers of righteousness; whose end shall be according to their works. I say again, Let no man think me a fool; if otherwise, yet as a fool receive me, that I may boast myself a little. That which I speak, I speak it not after the Lord, but as it were foolishly, in this confidence of boasting.
Seeing that many glory after the flesh, I will glory also. For ye suffer fools gladly, seeing ye yourselves are wise. For ye suffer, if a man bring you into bondage, if a man devour you, if a man take of you, if a man exalt himself, if a man smite you on the face. I speak as concerning reproach, as though we had been weak. Howbeit whereinsoever any is bold, (I speak foolishly,) I am bold also. Are they Hebrews? so am I. Are they Israelites? so am I. Are they the seed of Abraham? so am I. Are they ministers of Christ? (I speak as a fool) I am more; in labours more abundant, in stripes above measure, in prisons more frequent, in deaths oft."
Here, Paul was speaking about the same exact people "which glory in appearance, and not in heart" (2 Corinthians 5:12), or about those who "glory after the flesh."
Well, who were these people?
Here is what we know about them:
1. They were false apostles or deceitful workers who had transformed themselves into the apostles of Christ.
2. They were ministers of Satan.
3. They gloried "after the flesh,", which is the real issue behind your question.
4. They were bringing the people into bondage.
5. They were Hebrews.
6. They were Israelites.
7. Naturally speaking, but certainly not spiritually speaking, the were the seed of Abraham.
If you understand anything at all about the timeframe in which Paul was writing, and if you understand anything at all about Paul's primary combatants, then you will easily recognize that these people who "gloried after the flesh" were the Judaizers of Paul's day who sought to bring the people back into bondage by seeking to subject them again to the law of Moses and its accompanying circumcision in or "after the flesh."
Again, in context, this is what Paul was talking about when he said the following:
2 Corinthians 5:12-16
"For we commend not ourselves again unto you, but give you occasion to glory on our behalf,
that ye may have somewhat to answer them which glory in appearance, and not in heart. For whether we be beside ourselves, it is to God: or whether we be sober, it is for your cause. For the love of Christ constraineth us; because we thus judge, that if one died for all, then were all dead: And that he died for all, that they which live should not henceforth live unto themselves, but unto him which died for them, and rose again. Wherefore henceforth know we no man
after the flesh: yea, though we have known Christ
after the flesh, yet now henceforth know we him no more."
As I rightly said earlier, here, Paul was seeking to equip his Corinthians hearers with "somewhat to answer them which glory in appearance, and not in heart" or with something to answer the Judaizers of his day who "gloried after the flesh" in that they sought to bring the Corinthians back into bondage under the Mosaic law with its accompanying circumcision in the foreskin of one's flesh.
With this understanding, Paul went on to say:
"Henceforth," or from hereon, "know we no man after the flesh: yea, though we have known Christ after the flesh, yet now henceforth know we him no more."
In other words, our relationships with one another as Christians are not based "after the flesh" or after the Mosaic law, neither is our relationship with Christ any longer based upon the same. The law once foreshadowed Christ, and people knew him that way, but now that the body has come, we no longer need the shadows or foreshadowings.
This is what Paul was saying, and by no means was he denying that Christ had come in the flesh.
In fact, Paul regularly acknowledged in his epistles that Christ had come in bodily form.
Colossians 2:9
"For in him dwelleth all the fulness of the Godhead bodily."
Colossians 2:16-17
"Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath days:
Which are a shadow of things to come; but the body is of Christ."
Etc., etc., etc.