For safety reason the plane should be refuel first before to let the passenger to board the plane.. ridiculous instructions .

You always have to leave your seatbelts unfastened when there refuelling

I’ve never heard of keeping the seatbelts unfastened. At my airline (large US carrier), we have to keep the boarding door open with the jetway attached. Or, if there’s no jetway or boarding stairs available, we can refuel if all exit door slides are armed and ARFF is informed.