Hello, friend!
First, the HG633 is a carrier's device.
The ONT is a terminal device. Therefore, the CRC and FEC information of the ONT needs to be queried through the upper-layer device. The terminal device does not support this information.
If you use a Huawei OLT, you can run the display statistics gmac command to check the value of OMCI received CRC error, and run the display ont info command to check the ONT FEC status.
As mentioned above, the HG633 is a carrier series device. We have no right to view the device documents. If you need to configure ONT Telnet and SSH, you can log in to the device web page to check whether the device supports and configures the ONT. If the HG633 is not configured on the device web page, The device does not support Telnet and SSH. You need to obtain the solution from the ISP.
To log in to the H633, perform the following steps:
1. To log in to the HG633, use a cable to connect the HG633 to the PC, open the web browser on the PC, and enter the default IP address 192.168.1.1 in the address box.
2. You should now see the router login page with 2 text fields where you can enter your username and password
3. The default user name and password of your HG633 are admin.
4. On the login page of the router web page, enter the user name and password and click Login. The Huawei HG633 control panel is displayed.

For device software information, refer to How to download the software and firmware of ONT
Thanks!