You can take multiple TCS NQT attempts. However, as per official TCS iON guidelines, if you take a paid TCS NQT IT exam in February, you cannot repurchase and attempt the same paid variant in March because there is a 90day gap required before you can buy and retake the same test.

Regarding free NQT drives, TCS announces them separately, and there is no official 6month wait rule — eligibility depends on the specific drive and your graduation batch.