Did I overstay my visit ?

Hi, I was previously posted in this forum before but its not complete , unclear and I make some mistake information in my previous thread. Please just ignore my previous thread.

So I was previously studying here for 2 years and my school have taken my student pass and surrender it to ICA.
My student pass supposed to end by 13 december however as my course end early my school has already surrender my student pass and give it to ICA.

After that ICA give me a social visit pass letter valid from 31 october to 13 december which is the same date as my student pass end date.

It says

This documents serves as visit pass issued to the student under regulation 12 of immigration regulations. This visit pass is valid from 31/10/2018 until 13/12/2018 or the last date which students passport or other travel document is valid , whichever the earlier egulations. This visit pass is valid from 31/10/2018 until 13/12/2018 or the last date which students passport or other travel document is valid , whichever the earlier

And I go back to my country to take my document by 15 november for 3 days and comeback here again for applying Australian uni through my school in Singapore. When I come here they stamp my white card as usual.

*Everythings fine*

And Im going back to my country again 27 november and come back to sg 1 december to apply for my Australian visa as the nearest visa embassy located near my hometown is in Singapore. They also stamp my white card as usual

*Everythings fine* I got my Australian student visa granted


But I stay in sg until 15 december

So my question is does this consider as overstay ? Coz by what Im understand my previous visit pass will no longer valid once I leave sg and once I come here they give me another visit pass valid for 30 day stamped in the white card is it true ?


When Im going back at 15 december everything is fine , I go back to my country using the self machine passport control for immigration clearance and all is ok at that time. But im still confused wheter this is overstay or not im worried for my next visit to sg.

Im really scared as I dont want to messed with Singapore immigration.
I have booked a flight to Australia from Singapore and plan to stay in sg for 3 or 7 days for my next visit by next month

This get me really anxious I couldnt even sleep at night thinking about this
I ask my parents and other forum they say its fine but you know im quite anxious about this especially for my next visit there keep on dreaming of getting deported or something idk maybe I think too far

Thanks