4 Oct 2019
Equipment you control still have their other equip abilities in addition to equip Knight {0}.
4 Oct 2019
Whether the target creature is a Knight is checked only as the equip Knight ability is activated and as that ability resolves. If the creature somehow becomes a non-Knight creature later, the Equipment remains attached to it.
4 Oct 2019
Syr Gwyn's triggered ability triggers once per attacking creature that's equipped, regardless of how many Equipment those creatures each carry.
4 Oct 2019
If Syr Gwyn leaves the battlefield after an equip Knight ability has been activated, that ability still resolves even though the Equipment has lost that ability.