If, as Romans 8 tells us, God foreknew, predestined, called, justified, and glorified sinners, then no, there is no possibility that once saved, they could be lost:
NKJV Rom 8:28 And we know that all things work together for good to those who love God, to those who are the called according to His purpose.
Rom 8:29 For whom He foreknew, He also predestined to be conformed to the image of His Son, that He might be the firstborn among many brethren.
Rom 8:30 Moreover whom He predestined, these He also called; whom He called, these He also justified; and whom He justified, these He also glorified.
No. It exemplifies His sovereignty.
That is not so. As Martin said, God also appointed the means by which sinners should be saved, including hearing the gospel, believing on the Lord Jesus Christ, and repenting of our sins.
I don't believe so. Rather, I think you misunderstand what Martin and I believe, as we have both tried to tell you many times. Rather, you often seem to tell us what we believe, and that bears little resemblance to what we actually believe.