Explanation:

RBI acts as regulator and supervisor of the banking sector through the provisions of the Banking Regulation Act, 1949.
Focal points for providing framework for regulation

• Issuance of ‘licences’ for opening of banks
• ‘Authorisations’ for opening of branches by banks in India,
• governing foreign banks entry and expansion and approval of Indian banks to operate overseas,
• policy formulation, review and implementation on Prudential Norms, Basel – II and III frameworks, validation of quantitative models on Credit, Market and Operational Risks, Stress testing,
• International Financial Reporting Standards (IFRS), Securitisation,
• Resolution mechanism, etc.
• Monitoring maintenance of SLR and CRR by banks,
• Approving the appointments of Whole Time Directors & Part-Time Chairperson of Private Sector Banks and Chief Executive Officers of foreign banks operating in India, and their compensation packages.
• overseeing the amalgamation, reconstruction and liquidation of banking companies,
• policy issues relating to customer service,
• Anti-Money Laundering and Combating Financing of Terrorism and issuing of instructions regarding KYC
• regulation of financial institutions

According prior approval for acquisition of 5% or more of the shares or voting rights of Private Sector Bank

Hence option 4th is correct.