Paranoid about Malware/viruses

So recently I have been getting more spam emails and I have started to worry way to much about malware and viruses. I now find my self making myself anxious about everything (simply viewing video ads that aren’t from brands I know, downloading apps that are from smaller companies, etc). I factory reset my phone after I clicked one of the spam emails on accident but is there anything else I should know?

Is malware or viruses even possible on Iphone ?

How would I know if my device is infected?

How would I get rid of viruses or malware on my iphone?

Are there “quality checks” video ads on Tiktok and Youtube have to go through to ensure they don’t include viruses or malware?

Thanks!