Export FOC sales

Where FOC exports are to unrelated party then it would not be a supply under GST, although is an export of goods as the goods move outside India.

Where FOC exports is to related party it would be covered under Sch 1 Clause 2 therefore, covering under section 16 IGST Act - zero rated supply. 

Where the export is in relation to samples - then ITC can disputed although samples under Section 17(5)(h) can be read to be purchased goods - inputs and not finished goods.

Therefore, ITC reversal can be said as not required. Where value is high suggest you to obtain a legal opinion.