[Scenario]

Well, for the first one, it kind of depends on which command processor you're using. If you're using the standard, OnPlayerCommandText(), I think this would work:

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
    if(pLogged[playerid] == false)
        return SendClientMessage(playerid, COLOR_RED, "ERROR: You aren't logged in yet, moron!");

    return 0;
}

If you're using ZCMD/y_commands, you could do this:

pawn Код:

public OnPlayerCommandReceived(playerid, cmdtext[])
{
    if(pLogged[playerid] == false)
         return SendClientMessage(playerid, COLOR_RED, "ERROR: You aren't logged in yet, moron!"), 0;

        return 1;
}

As for the second thing: just learn how to use SSH to start/stop the server, and how to use "nano" to edit the server.cfg.