Re-entry to Singapore

I got a job offer in SG and my employer applied for an Spass.  The status was still pending a day before my 30-day visit expires.  So I decided to exit another country. During my 4 days stay in another country, my Spass got approved and the employer emailed me my IPA. 

When I go back to SG, should I declare to immigration that I just got my IPA? Is it ok to show them the copy through my phone?

The immigration offices will be able to see your complete application and visa history on the screen in front of him. Showing your passport (and possibly telling your FIN number) is sufficient.