Q1. You should calculate tax based on ticket prices. Input if charged by suppliers you can claim full credit on all expenses you mentioned. If suppliers are unregistered then you have to pay tax under RCM and after payment you can claim input tax credit.
Q2. You need to file all returns you mentioned.
Q3. GST tax rate for cinema halls showing movies is 18% (9% CGST and 9% SGST ) for tickets priced below Rs. 100. For ticket priced above Rs. 100 GST tax will be 28% (14% CGST and 14% SGST).