Please follow :

How to get node properties and populate in page using Sightly API

Creating system users session in AEM - Getting system user session in AEM

Create system users from console http//localhost:4502/crx/explorer

User 1 : shasservice - user with no access permissions
User 2 : serviceuser - user with all the access permissions

Please follow here : Creating system users session in AEM - Getting system user session in AEM

Thanks
Sony C