If instances of an application send ReceiveMessage request at the same time for SQS is it possible for them to receive the same message?

In a distributed system, race conditions can occur that make this possible, or better said, it is not impossible. Idempotency is the solution.

SQS was designed with the architecture you describe in mind - auto-scaled fleets of worker instances all consuming the same queue are a very common pattern. Receiving the same message is rare (I've never seen it when looking through logs); there's probably no guarantee though and this possibility is covered by the declared at-least-once delivery.