1031 Exchange Question

There are two parts to the 1031 exchange process that I was not clear on, particularly-

Property Identification -Post closing of the first property, the Exchangor has 45 calendar days to identify to either the accommodator or the closing entity the addresses of the potential replacement properties. In a reverse exchange where either the replacement or relinquished property is parked, the Exchangor has 45 days to submit a final list of properties for sale or purchase.

and

Within 180 calendar days following the closing of the first property or extension of the Exchangor's tax return, the property must be purchased.

Let's say that I'm exchanging a single property for multiple rental properties. Does that mean that once the single property has been closed on (meaning the money is in escrow?), I now I have 45 days to identify properties that I will exchange and have 180 days to close all of them? What if one of the properties I identified doesn't end up selling to me? Especially when you're exchanging a single property for up to 5-6 properties, how does one guarantee that the 45 day list requirement is met? Thank you!