To determine the minimum institutional requirement for NAAC accreditation cycles, particularly for the second and subsequent cycles, we need to evaluate each provided option against official NAAC guidelines.

1. Option: Submission of SSR only; IQAC is optional
   • An Institutional Accredited Grade (IAG) can be understood as maintaining quality standards. However, the submission of the Self-Study Report (SSR) without an Internal Quality Assurance Cell (IQAC) does not align with the NAAC's focus on continuous improvement.
   • The IQAC is crucial for maintaining the momentum of quality consciousness in institutions, making this option invalid.
2. Option: Only achieving B⁺ or above in previous cycle
   • As per NAAC guidelines, institutions must have secured at least a B⁺ grade in the previous cycle to apply for subsequent accreditation cycles. This ensures that the institution has met a satisfactory quality benchmark previously.
   • This option correctly reflects the minimum requirement, making it the correct answer.
3. Option: Functional IQAC and timely submission of AQAR
   • While a Functional IQAC and the timely submission of the Annual Quality Assurance Report (AQAR) are important components of maintaining accreditation between cycles, they are not explicitly cited as minimum entry-level requirements for applying again.
   • Such elements aid in the continual quality improvement process, but they are part of the broader quality process, not the minimum criterion for re-accreditation eligibility.
4. Option: Participation in NIRF ranking in the intervening years
   • The NIRF ranking system, although beneficial for benchmarking and improvement, is not an explicitly required criterion by NAAC for re-accreditation.
   • This option does not satisfy the minimum institutional requirements for NAAC cycles.

In conclusion, the minimum institutional requirement for an institution to proceed to its second and subsequent NAAC accreditation cycles is only achieving B⁺ or above in the previous cycle. This directly aligns with the NAAC's quality assurance focus on maintaining minimum quality standards from cycle to cycle.