Hoarding Broodlord

If a creature you control has a mana ability with {T} in the cost, activating that ability while casting a spell with convoke will result in the creature being tapped before you pay the spell's costs. You won't be able to tap it again for convoke. Similarly, if you sacrifice a creature to activate a mana ability while casting a spell with convoke, that creature won't be on the battlefield when you pay the spell's costs, so you won't be able to tap it for convoke.

When calculating a spell's total cost, include any alternative costs, additional costs, or anything else that increases or reduces the cost to cast the spell. Convoke applies after the total cost is calculated. Convoke doesn't change a spell's mana cost or mana value.

As long as that card remains exiled, you may look at it. This remains true after Hoarding Broodlord leaves the battlefield.

If another player gains control of Hoarding Broodlord, it's still you who can look at and play the exiled card. That player won't be able to look at or play the exiled card.