1. For exempted goods/services there is no charge of gst only, therefore no need to pay gst on advances received. In gstr - 1, there is a seperate head only for details of exempt supplies supplied.
2. For goods/services which attract gst and advance is received for such goods/services then the payment of gst need to be done for the month in which advance received within the due date. That is 20th of next month while filing gstr - 3B. Further in Gstr - 1 you will find a head for advances received, there you will have to fill the details of advances received.
Advance on Supply of Taxable Goods: As per Notification 45/2017 CT , Advance reced on account of supply of Taxable Goods is being deferred for Regular tax payer (composit dealer is liable to pay tax on adavace reced)
Advance for Supplies of Taxable Services : Yes GST is levy on advance reced on account of supplies of Services.
Advance for supply of Exempted Goods & Services: when there is no tax on supply of goods & services for which advance is reced then how can be gst attracts on advance for such supplies . hence no GST attracts on advance reced for supply exempted goods or Services