I just send BTC from my electrum wallet to Changelly so that I can convert to altcoins 8 hours ago, but I set my transaction fee to low (5 satoshi per byte), it is still zero confirmation as at right now.

What i want to know is, as long as there is one or two confirmation (doesn't matter how long), I will receive my altcoins, right? Or is there a window of payment?

Will they return me my BTC if somehow after 72 hours they still don't receive my BTC or something