Applications Remediation after upgrade from 7.0.2 to 8.5.2: what is important to check?

We are planning the upgrade from Lotus Domino 7.0.2 to 8.5.2.As a developer I have to identify the list of the issues in the applications that must be remediate before the upgrade by a design change. For example, I am looking for any code that is no more supported or not working as expected after the upgrade or anything that may affect the applications.

Thank you in advance for your tips !

Subject: Applications Remediation after upgrade from 7.0.2 to 8.5.2: what is important to check ?

We checked our apps thoroughly for an update from 6.5 to 8.something and the only thing we found was that InputEnabled formulas did not work quite right with Native OS style fields. If I recall correctly they did not detect whether the form was in read mode or not. We adjusted the formulas a little and all was well.