You still pay all costs and obey timing restrictions when casting Undead Sprinter from your graveyard with the permission from its last ability.

If Undead Sprinter is countered or dies after being cast from your graveyard, it will return to your graveyard. It may be cast this way again.

Once you begin casting a spell from your graveyard, it immediately moves to the stack. Players can't take any actions until you've finished casting the spell.