SC Application - Get married during Approval-In-Principle period

[eyesyen]

Online submission: 03-04-2017
Appointment date: 24-08-2017
AIP letter date: 07-02-2018 (SC journey two months up to 06-04-2018)
Away from SG for CNY: 14-02-2018 to 20-02-2018
Registered for CSS: 07-03-2018
ROM at Malaysia: 17-03-2018
Registered for SET: 24-03-2018
Away from SG (vacation): 27-03-2018 - 03-04-2018
Wedding buffet at Malaysia: tentatively June 2018

Referring to the above summary, I have a few questions:

i) Do I need to update ICA after ROM? When is the best date? Is there a need to submit the marriage cert in order to get another official copy of marriage cert in Singapore?

ii) As I understand, once the SC Journey is completed, I'll have to wait for about 3 weeks to receive the approval letter, meaning that it will be around end of April. Lets say if all the remaining procedures (surrender Malaysia citizenship etc) will be completed on May, will this affects the marriage cert? In short I am concern if there will be any impact if I have the changes of citizenship after getting married about two months.