I think the parallels between physical birth and spiritual birth (which is what is meant by "born again"--see John chapter 3) are quite apt. And just like physical birth can be neither reversed nor repeated, the spiritual "new birth" can not be reversed or repeated. Now, there are plenty of cases of someone who believes falsely that he has been saved or born again, who subsequently experiences the real thing.

There's no evidence in the Bible that anyone was ever 'born again' again.

No. to me, its like a person who commits a crime, and is put on probation to prove ones self. violate the probation and you do jail time. born again twice is like saying "i can do this, i can do that. its ok. all i have to do is be born again a 2nd, a 3rd, a 4th time. maybe criminals think this way. its why they continue to commit crimes, knowing they will be forgiven. don't think so! one day they will have to answer for their actions and hell ain't half full........a second chance is just that and no more.

No. While it is questionable whether a person can lose their salvation, what is clear is that if you can lose it, it's impossible for you to get it back. Hebrews 6:4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, 5 And have tasted the good word of God, and the powers of the world to come, 6 If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame. Observe that if a person "could" lose their salvation by willful sin against God there would be "no more sacrifice for sins." (v. 26) Hebrews 10:26 For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, 27 But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries. 28 He that despised Moses' law died without mercy under two or three witnesses: 29 Of how much sorer punishment, suppose ye, shall he be thought worthy, who hath trodden under foot the Son of God, and hath counted the blood of the covenant, wherewith he was sanctified, an unholy thing, and hath done despite unto the Spirit of grace? 30 For we know him that hath said, Vengeance belongeth unto me, I will recompense, saith the Lord. And again, The Lord shall judge his people. 31 It is a fearful thing to fall into the hands of the living God. However, as the end of the chapter concludes, someone who would willfully sin like that apparently never believed with saving faith to begin with: Hebrews 10:39 But we are not of them who draw back unto perdition; but of them that believe to the saving of the soul.

in this world u can not be born again ..but as this world is a test for humans and all creatures will alive again and they will be given their results of what they have done in this Hereafter or domesday..if a person done good deeds he will rewarded heaven and if a person done bad deeds he will be sent to hell

As many times as you want since people seem to believe they save themselves.