H1b extension query


My h1b is valid upto December this year but due to commitments I could not travel till now?. Pls help with below questions

1)how soon before h1 expiry I need to travel to apply for extension
2)can I apply for extension from India even without traveling to US?
2)in case I cannot travel before expiry date, do I need to start all over again i.e., do I need to go through lottery system again