Final Fantasy 15 Noctis – Does Noctis Take Fall Damage?

From my experience, you will be unable to parry (despite the prompt making you think that you can) if you are still carrying out an attack. This has been the most common reason I've failed parries.

1. I can confirm that what direction you are facing will not prevent you from being able to parry an attack, as I've parried attacks that were coming from behind, simply by holding the Square button. As long as you have the Square button pressed when the attack hits you, you should parry successfully.

2. The time window varies with enemies, as they attack at different speeds. For instance, I've parried the Slime-type enemies (Flan, etc) by holding down the Square button as they approached and it's taken up to 10 full seconds before I actually parried (if not more) as they approach very slowly. For faster enemies like a Coeurl, you will have less than a second to react, and, from experience, if you're mid-attack at all, you won't make it. Using quick weapons like the shortswords will give you a better chance to successfully pull off a parry. Using a greatsword, on the other hand, results in very few successful parries.

3. As to whether or not parrying is worth it, definitely. I have survived many fights that my party members have all died during simply because I stopped attacking and just parried everything I could.

The Break Damage Limit is only available for Links and tech, and is not possible to achieve with standard attacks sadly