What is the ruling on uploading lecture recordings and sharing them with students after the professor's approval for recording only, without his approval for publishing or circulating them, and what is incumbent regarding recordings that have been uploaded previously?

There is no objection to uploading lectures that have been permitted for recording, for the purpose of benefiting from them, so long as their owner has not prohibited their dissemination. The default for lectures is that they should be disseminated for people to benefit from them. Permission to copy implies permission to utilize them, and customary permission takes the place of explicit permission.