Can I run 2 WordPress website and 2-3 sub-domain in 1 VPS Hosting?

Frankly, I think you may need to choose a managed hosting provider instead. Cloudways allows you to run on top of DigitalOcean and gives you what you actually want functionally but you will pay more. #1 & #3 - Yes you can, but you need to configure and install everything yourself, no CPanel here (unless you install it!)

Think of DigitalOcean as a true “DIY” setup. It can accomplish what you want, but not the way you want things done for you and supported. You will have to work at the linux level and manage your own OS install(s) of wordpress, same with your DNS entries. While you will find there are plenty of helpful DIY answers here, you may want to try running this in virtual machine at home until you feel comfortable with it.

#7 Look at the pricing, there’s usually some kind of promotional credit, but ultimately it is a metered service with minimums. Like your electric company, you pay for what you use and there’s always a minimum. If you use a lot, you’ll spend a lot. The prices are highly competitive and around the lowest I’ve seen for the features provided.

#8: you can’t really run one instance of WP on this, but DigitalOcean will not stop you from trying, but when you have issues, you must solve them… remember… DIY. Minimum would typically be a 2GB instance.

All in all, I would say your minimum would typically be about $250 minus backup storage where, again, you pay for the space you use.

No one laughing at you, maybe at the friend who sent you here… Best to look at Cloudways instead running on DigitalOcean. You’ll pay more, but frankly you want more done by others.