Advance Salary provided by employer against covid - whether I have to give them the salary back?

During the lock down period our company has provided a salary as advance against covid and that also of fifteen days. My question is that whether they can ask for salary to be deducted how the same is treated in other organisations whether I have to give them the salary back.

If the company decides to pay you full salary, then the advance already given to you will be deducted from the salary and the balance will be paid to you. If the company decides to pay you 50% salary during lockdown period, the salary will be processed considering the advance already paid as advance and account settled without paying anything by way of salary. If the company decides that during lockdown period there was no work and hence no salary shall be paid, then the advance paid should be given back either in installments by way of deduction from salary due in post lockdown period.