When it is free from charge
Correct — If a Fixed Deposit is not pledged or charged to the bank, it represents a clear debtor–creditor relationship, and a garnishee order can be applied.
Only to surplus margin if pledged
Correct — When an FDR is pledged as security for a loan or overdraft, the bank has a prior right of set-off. The garnishee order applies only to the surplus amount, if any, after covering the bank’s dues.
Even if fully secured against loan
✖ Incorrect — If the Fixed Deposit is fully secured against a loan, there is no surplus available. Therefore, the garnishee order does not apply.