What is the ultimate spiritual goal mentioned in Chapter 16 of Sai Satcharitra, and what is the primary method prescribed to achieve it?

The ultimate spiritual goal described in Chapter 16 is attaining 'Sayujya,' which means union with Brahman or the ultimate reality. The chapter is unequivocal that the primary, and indeed only effective, method to achieve this is through the devoted service of the Sadguru. It explicitly states that by serving the Guru with faith, the servant attains this union. Furthermore, it cautions that all other means will fail. The key elements of this path are having firm faith at the Guru's feet, avoiding any neglect or cleverness in service, and surrendering completely, as the Guru is the one who provides the remedy for the disciple's unseen pitfalls.