Is the prayer valid if the worshiper suddenly lifts his head from prostration after saying "Subhana Rabbiyal A'la" twice, because a small cat jumped onto his head, then he sat upright and performed the second prostration, and did not interrupt the prayer?

If you rose from prostration due to fright and did not intend to rise yourself, then this rising is not considered valid Islamically, and your prayer is void. You must repeat it due to abandoning the pillar of rising from prostration. Glorifying Allah during prostration is sufficient once, but it is better to do it three times.