Not necessarily -- there can be a number of reasons one can access localhost over the loopback interface that does _not_ imply root access: SSRF, misconfigured

Not necessarily -- there can be a number of reasons one can access localhost over the loopback interface that does _not_ imply root access: SSRF, misconfigured tunnels, or just a plain unpriviliged account where the attacker couldn't perform privilege escalation (either because the attacker's incompetence or the system being up-to-date and/or hardened)