Rcm on gta

this means transporter can not avail credit if he want to supply service by selecting RCM applicable Yes....

or he may take credit on supply received and charge 12% in invoice as normal taxpayer

Answer to your first & second para is you are eligible to claim ITC for a GST amount you had paid under RCM. Answer to your third para is if a transporter intends to claim ITC against his input services received, he himself paid GST Amount @ 12 % under forward charge and not intends to claim ITC , he himself paid 5% GST under forward charge.

the matter u are talking about is only for transporter....if u pay RCM then u will be eligible for credit....and u can claim credit whether u have paid 5 % or 12%....
and second thing...u can claim RCM in that months only...u dont have to wait for next months...u can claim input in which u have paid RCM😊