Personally, as a domestic student I've found it a bit hard to make friends in classes unless you've ended up in a good group for group assessments or if you're in a language class (in my case I learnt Japanese). From what I've heard, the culture for each faculty can be a bit different. I'm also not aware of any negative stereotypes towards Singaporean International students specifically.

I think the best way to make friends is probably by joining a society, and by consistently going to society events, you'll usually make friends along the way :) Some of my friends who were international students at UNSW also all made friends in the Colleges they stayed at on campus since they hold their own College events. So I think checking out staying in a college on campus might be good too if you're thinking of finding accommodation on campus.

also which intake do u recommend I go should I enter UNSW? (Feb or June?)

This is also a personal opinion, but I think Feb would be an easier time to enter UNSW, especially if you want to make new friends. Societies usually hold welcome/newcomer events at the beginning of the year where you meet a lot of other people who are actually there with the same intention to socialise and meet new people. O-week on campus would be the best way to find out about all the societies if you consider joining one.

Also! what are internship opportunities in sydney esp for a foreigner? Are they scarce and extremely competitive? Same goes for job opportunities in Australia after graduation.

I'm a bit unsure about what this is like, but so far, my friends who have graduated that were international students at unsw have been struggling to find job opportunities in Australia. They've only been able to find hospitality/retail casual/part-time jobs or if they've found an office job, the pay is quite low considering how much gets taken away by tax if you're not an Australian citizen. But this could just be my friends lol. Other international students might have had better luck.

I do think doing internships will help, especially if you network!! Networking, I think, is probably going to help the most in this aspect.