Djeru and Hazoret

If the spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.

If you cast a spell without paying its mana cost, you can’t choose to cast it for any alternative costs. You can, however, pay any additional costs. If the spell has any mandatory additional costs, you must pay those.

Once Djeru and Hazoret has legally attacked during the turn it came under your control, causing it to lose haste by adding cards to your hand won’t cause it to stop attacking. Similarly, causing it to lose vigilance after it has attacked won’t cause it to become tapped.