Isn't possible giving sheet level using Section Access script instead of doing in QMC?
No, Section access is applied on data model itself. Unfortunately, you can not do that.
Many threads discuss how to achieve this; please refer to:
Sheet or App Object Level Security Qlik Sense
Sheet level Section Access in Qlik Sense ??
Sheet level access
QlikSense Sheet Level Security - QMC Security Rules
Retrieving data ...