I am claiming my pension before top-up eligibility age. Will I get the top-up at a later date?

Yes, if you claim your pension without a rate reduction, but it will only be added on automatically once you have reached age 55.

For the record, if you claimed your entitlements prior to 2021, the top-up will be added on when you reach the full-rate eligibility age for the year of your claim (see summary table of pension claim rules).