关于GP12的开始时间和检验频次问题

最近在看GP12的标准，有两个问题向大家请教：

1、标准中”B. Plan Development: Development of a Pre-Launch Control Plan which is a significant enhancement to the production control plan and also consisting of additional controls, inspections, audits, and testing to insure conformance and capability of the manufacturing process. The plan needs to consider; 1. Increased frequency/sample size as stated in the Production Control Plan.“
是要求在试生产控制计划或量产控制计划中增加检验频次和抽检数量吗？在网上搜了一些关于GP12的程序，没有上述要求。

2、GP12的开始时间是什么呢，样件、小批量试生产还是量产初期？有些公司规定P1/P2/SOP阶段还有SI/S2/SOP阶段还有TT0/TT1/SOP阶段，不太明白代表什么意思，请大家指教。