MX with EOP

MX>

1, cotonso-c0mi.mail.protection.outlook.com > 213.199.154.87, 213.199.154.23

100, mail.messaging.microsoft.com >207.46.163.247,207.46.163.215,207.46.163.138

Hi,

I would like find out some information and clarification with above MX record setup

1) Do EOP setup always can add mail.messaging.microsoft.com as secondary MX record?

2) What if on premise Exchange not available, do the EOP retry send for 48 hrs?

3) Are the 2 MX record work the same on resending and retry in the event on premise Exchange not available?

4) Is this a recommended way or best practice?