Can I CLAIM Unclaimed ITC as per ANNUAL TAX LIABILITY & ITC STATEMENT SUMMARY IN MARCH

Yes claim ITC and also make proper reconciliations for the same.

Thanks Sourav & Altamush Zafar. 

Yes you can claim ITC

I am getting this message when I entered anything more that is available in GSTR2B for the quarter (Jan-Mar21).
"The information entered by you in cells highlighted in red is in variance with the auto-populated data in table 4A. The input tax credit has been auto-populated based on the GSTR-2B generated for you. Also, please note that any variance above 5% of the input tax credit is in contravention to Rule 36(4) of the CGST Rules, 2017. Kindly recheck and proceed."
Can I still CLAIM all the unclaimed ITCs as per ITC SUMMARY (2020-2021)

Yes you can still claim. Prepare proper reconciliations so that you can explain to the department when needed.

Ok. I'll claim them. Thanks for your help.