Questions about H1B Visa Stamp - Thank you!!!

I will go back Beijing to apply for H1B visa stamp (1st time).
I have 2 questions regarding H1B visa application:
1.The effective date of my H1B petition is Oct1, can I apply the visa at the end of August?
2.Once I get the H1B visa stamp, when I can enter the US on H1B status? do I have to wait until on or after the effective date, which is Oct1 to land in US or I can enter the US several days before Oct 1 on H1B visa.

Please advise. I appreciate your time and help very much.