The 4 spheres if I understand you correctly are your parents, Buddhas and Bodhisatvas, all sentient beings, and your nation. When you are offering prayers, you are offering to those. In a way to say you are honoring and thankful to your parents, to Buddhas and Bodhisatvas, all sentient beings, and your nation. Parents have brought you here, Buddhas and Boddhisatvas are your teachers and guidances, you are related to all sentient being through a special relationship such as the clothes you wear were made in China by the Chinese for example or the food that you eat brought to you by the farmers, and lastly your nation or country support you in many ways.
NAM MO A DI DA PHAT (VIETNAMESE)
NAMO AMITUOFO (CHINESE)