Both OK. But it is used in different scenarios. It depends on what information do you want to highlight in this sentence. We always put the most important information in front of the whole sentence.

我个人觉得第二句逻辑有点反了，不过不会影响到理解这句话的意思，用第一句逻辑思维清晰

老板半个小时以后回来VS半个小时以后老板回来

Yes. In Chinese, "time" is often the first thing mentioned in sentences like this. (I just joined italki and haven't finished my profile but I'm a fluent Mandarin speaker after living in Taiwan for 7 years).