Ok, so at Level 1, the Unbreakable Archetype has Tough as Nails, which says, "An unbreakable gains Endurance and Diehard as bonus feats. This ability replaces the fighter’s 1st-level bonus feat." Since both feats are still bonus feats, can I retrain the Diehard away at Level 4 for a different feat?
If so, what happens at Level 5 when I get Heroic Recovery as a bonus feat in place of Weapon Training 1? Do I still get it even though I no longer have Diehard, which is a pre-req? And if I still get it, can I retrain Endurance at Level 8?
You cannot retrain them. They are not "Fighter bonus feats", they are those feats specifically. Therefore no other feat would qualify. Diehard is the only feat that is Diehard, so there is no other feat that you could retrain it as. Moreover, as they are not "Fighter bonus feats", they do not qualify for retraining either. This is my interpretation.
As to your second question, You must retain all prerequisites when retraining feats.
Thanks. :)
If they are not fighter bonus feats, then what are they?
"Archetype bonus feats?"
it is just an untyped bonus feat instead of a "Fighter Bonus Feat".