You can register .ro domains and every Romanian extension (.com.ro, .info.ro, .org.ro, .store.ro and more), plus international ones such as .com, .net, .org, .e...
Yes, provided both domains are available and you meet the requirements for each extension. They are registered separately: owning the .ro name does not automatically reserve the .com version. Each domain has its own expiry date and needs to be managed and renewed separately.
To use both for one website, choose a primary domain and set up a permanent redirect from the other. Simply pointing both domains to the same IP address does not create a redirect: the web service also needs configuring, including a valid TLS certificate for each name accessed over HTTPS. If you also need email, configure it separately for each domain.