Liable to pay gst by transporter

If such transporter is a GTA, then not required to collect and pay GST because RCM provisions would kick in. If not GTA and registered under GST, then GST to be collected under forward charge and paid to the govt (in case of taxable services).

If a transporter has GST Number then he can opt either to pay tax @ 12% and claim ITC or he can opt not to claim ITC and then RCM will be paid by recipient.

Only one choice can be made. Therefore it is not necessary that if GTA has GST registration then he has to collect GST. He has both the option

Depends upon whether the transporter has opted for 5% tax scheme or 12% tax.

if it has opted for 5% tax scheme then he would not pay any tax. the person paying freight will hav to pay tax under rcm.

the transporter must indicate this in his bill-t or in any other manner. if the status of transporter is not known then it is recommended to first get the relevant information from transporter and only then file your return.