The problem is that there is no control panel on the hosting.
SSH (English Secure SHell - “secure shell”) is a session-level network protocol that allows you to remotely control the operating system and tunnel TCP connections (for example, to transfer files). It is similar in functionality to the Telnet and rlogin protocols, but, unlike them, encrypts all traffic, including transmitted passwords.
It is safe and convenient! Your hosting website should have instructions for connecting via SSH. Details can always be found in Google.
On the hosting site, of course there will be no panel, since the connection is made via SSH clients: PuTTy, OpenSSH
Depends on what is considered full.
Normal administration of * nix-systems - yes, of course, they usually do this. SSH allows you to execute commands (in particular, run editors to edit files), panels do the same (from a fixed set of commands and file changes).
But if you break the system in such a way that it stops loading - for example, unsuccessful updating of the distribution kit - sshd will not start and more other measures will be needed. In traditional iron, it is usually IPMI; XEN'ovyh and KVM'nyh virtualok - VNC or telnet-access to a virtual terminal or COM-port; all OpenVZ is becoming more and more difficult up to the impossibility of fixing the malfunction on its own (then only the hosting support, and not the fact that it will be compliant).