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Giving a creature first strike works, but using the spell as a copy won’t do anything during combat. You’ll copy the spell off regular combat damage, creature gains double strike, but they’ve already passed the first strike damage phase of combat, so it’s dead after the first use
The creature doesn’t sacrifice it self to cast the spell, and the way checks during combat work, if you give you self Double Strike during the combat step you deal damage with First Strike, you do damage during both combat steps.