I did answer your questions.
YOU haven't answered this one:
What PRIZE was Paul telling people to STRIVE for, and cautioned them against being robbed, disqualified or deprived of?
When Paul speak of one's REWARD/PRIZE, he is, typically, not speaking of salvation, as he does here ...1 Corinthians 3:11 For other foundation can no man lay than that is laid, which is Jesus Christ.When Paul speaks of salvation, he clearly refers to it as a free gift, ... as he does here ...
12 Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble;
13 Every man's work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man's work of what sort it is.
14 If any man's work abide which he hath built thereupon, he shall receive a reward.
15 If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire.Ephesians 2:8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
9 Not of works, lest any man should boast.