How long does the visa extension process take for a 50-year visa in Phuket, and can dependants apply during this period?

The post asks about the processing time for the first extension of a 50-year visa in Phuket, the possibility of re-entering Thailand during the initial three-month period following the visa issuance, and the procedure for dependants applying for their visas during that time. It seeks clarification on whether dependants can receive their visas after the main visa holder's extension and if they can all extend their visas together for one year.