Visit/Tourist visa

1. What will be ideal period to apply visit visa??
2. What are chances of rejection?
3. Any additional information regarding this situation?

To answer these questions:

There is no ideal period to travel here. You didn’t mention whether it will be first time to visit here or earlier you had visited!

You can visit here but should have return ticket (1 week or 2 weeks) and hotel or address of the place you will stay along with contact details. You should tell the rationale to visit here, if in case officer asks.

Three times students pass is not a good thing but it may not have direct impact on your tourist visa application approval. Good luck

This is my first time to apply for tourist visa.
I meant to ask that my student pass rejected 10 days before so what is ideal period of applying tourist visa. Should I apply immediately or wait for month or more?

I will be living with my Fiancée and am planning to stay for 25days and with return ticket booked in hand.

Just little but worried about rejection due to earlier student pass rejection.

You will be staying with your fiancée! Are you both applying tourist visa or she is working or studying here? What’s her visa status? Next time, give proper details before someone can suggest anything.

Sorry for incomplete information.
My fiance is on Student visa.  She already in Singapore doing her study.
Only I am going to apply for tourist visa.

You did not mention why your student visa was rejected. Since the three rejected applications must have been for different courses/schools, I suspect this must be because of you - and thus might also affect a tourist visa (e.g. if you are somehow an unwanted person here, or they suspect you of having other motives than studying - which is confirmed by you having a fiancee here!).
It does no further harm to apply for an SVP for a short visit, but if that is also rejected I suggest you wait with any further attempt until you are married and can apply for a DP.

In my first application, college made mistake in application. They did not show my work experience and show gap of 9 months and also made mistake during academic qualifications.
While I applied again with same college and other course without rectifing mistake so it again get rejected.
So I applied with post graduate course in new college and rectify all mistakes. But due to previous rejection might be it get rejected again.
I will see of social visit pass and also some links of  job from India

Thank you very much

Giving contradicting information in a subsequent application without clearing up the first makes the authorities believe you are a cheater - or at least they do not know which information you gave is correct and which false. Therefore, all applications are rejected in such a case.
If you still want a visa for Singapore, you better contact them and clarify the issue, optimally with written proof that it was the school‘s fault.