You can't simply unequip Equipment from a creature. If Lightning Greaves is attached to the only creature you control, you won't be able to attach other equipment to it (or target it with anything else) until you have another creature onto which you can move Lightning Greaves.
07-08-2020
wotc
If a creature enters the battlefield under your control and gains haste, but then loses it before attacking, it won't be able to attack that turn. This means that you can't use one Lightning Greaves to allow two new creatures to attack in the same turn.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.