I understand that per the rules: a character can't use a feat if he loses a prerequisite. But what are the rules for selecting a new feat when a prerequisite is not part of you (such as an ability granted by an item or temporary power that is not always on). This part isn't clear.
For example:
Case 1: Improved Two-Weapon Fighting feat requires TWF and a 17 DEX
So what if my natural Dex of 15 was improved by a +2 stat boosting item? OR TWF feat granted by a rage power.
Case 2: Final Embrace feat requires the constrict ability.
So what if it's an item such as Anaconda Coils that grants the constrict ability?
Some feats have prerequisites. Your character must have the indicated ability score, class feature, feat, skill, base attack bonus, or other quality designated in order to select or use that feat.
Must the prerequisite be intrinsic in order to select that feat?