Do we have to show proof of marriage within 3 months of applying for a Resale flat under Fiance-Fiancee scheme to be eligible for the housing grant?

Have applied for a Resale flat under Fiance-Fiancee scheme and would be getting the keys in getting keys in Feb 2021. Recently got to know that for Resale purchase under this scheme have to register marriage within 3 months.

However the "auspicious" date we've chosen is in late 2021.

If we don't produce the ROM certificate within the 3 months, would it affect our Housing grant or any other implications? Anyone been through the same experience?

Thanks in advance.