Opening design for a 500 cubic meter vertical fixed-roof storage tank

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This is my first time dealing with storage tanks, so I have a few basic questions. I hope those who are more experienced will kindly offer their guidance: I have chosen a vertical storage tank with a fixed roof. 1. Provide side manholes, top manholes, and light-transmitting holes, as well as a cleaning access at the bottom of the tank. Is it too much? Is it sufficient to have a light-transmitting hole at the top plus an access hatch on one side? 2. How is the design pressure of the equipment determined? Is the design pressure for storage tanks of diesel, kerosene, and gasoline equal to atmospheric pressure? 3. Regarding nitrogen sealing: is it necessary to use a nitrogen seal to prevent the exhaled gases from reaching their explosive limit and causing an explosion? This is for safety reasons. 4. From a process perspective, is it still necessary to maintain a slight positive pressure to prevent excessive evaporation?