Should we answer these questions independently or together?

Both. Answer independently first (shows what you actually think, not what you assume your partner thinks). Then discuss answers together (reveals surprises and disconnects). The independent answers are usually more honest.

What should we do if we disagree on many answers?

It depends on which dimensions. Disagreement on trivial questions (favorite vacation type) is normal. Disagreement on core issues (parenting philosophy, financial goals, fidelity expectations) signals incompatibility or poor communication. Consider couples therapy to understand the gaps.

How often should we revisit these questions?

Every 5 years minimum. Major life changes (promotions, loss, health issues, kids at new stages) shift compatibility. Questions you answered the same in year 1 might have different answers in year 10. Regular check-ins prevent drifting into incompatibility without noticing.