Can discount rates use the country’s inflation rates, instead of using rates such as 3-6%, as indicated in some guidelines?

First, it is likely these will be similar numbers. Second, there may be problems comparing the studies with others globally because it’s common that most HTA guidelines around the world recommend around 3% for discount rate when comparing VFM of interventions in your country and other countries because the difference may not be about cost or effectiveness but the discount rate.