Lemmy instance on oracle free tier?

And just for a friendly reminder: oracle is hardly the only cloud provider that will boot you for being suspicious, according to the parameters they've determined as suspicious. Everyone does it and automating detection and mitigation is the path pretty much everyone at the medium or larger scale has taken and thus you're at the whims of a bot and an agent whose training is almost certainly to look at the score they have and then tell you no.
You should ALWAYS keep backups when renting someone else's computer's basement because even the "good" providers can decide you're a problem and boot you with no recourse.
That said I've used them for nearly a year and a half with no issues, but I also signed up from the US, with a non-debit/non-prepaid card, haven't used a VPN to access their services, and aren't running VPNs or proxies or torrents or portscanning or anything like that on the instances themselves.
...but I do at least once-a-day backups because even if you stay within their rules, there's nothing saying Larry can't decide tomorrow they're not going to offer this anymore and rug pull.

I'm doing that. 4 core arm instance with 24GB ram. It's on a paid account but using free tier.

If it's just for you, try it out, no harm no foul. If you are planning on hosting for other people then it's way too volatile, people will depend on your service to get access to Lemmy