Sorry for the rant! But try to explain with your words or with Google Translate how exactly have you progresed Billy's path?
183. Next day at school speak again with Billy about the lens.
a) He will ask 300$
b) "Have fun with mom" (for this option you need to have sleep mask in inventory).
258. Next day after school talk to Billy. Choose "Convice him not to go home". There are 2 options:
a) you can give him the coupon. This way you will keep him away from Janice in future.
b) tell him about mom at the beach. This way he will be involved in future events( NOT in 0.17 version ) with Janice.
319. Next day, after the school approach the Billy and ask about the plumber tools. He will give two options:
a) Bring him a poster with night elf priestress. To get the poster you need to use your PC and "search the web".
b) To bring a picture with Jason and Janice having sex. To get the picture you need to go to the pool and get into the threesome with Janice and Julia. There will be option to take a picture (need 350+ score with Janice). This option will also progress the Billy's path.
c) You can bring the poster to Billy and after take a pictures with Janice and just keep it for yourself. Pictures will apear at PC in the photolibrary only, they will not appear in the inventory.
343. Next day after school talk to Billy. Now you can repeat H-scene with Rachel in her bedroom.
a) *Optional* if you done previous Billy's path tasks, you will have option to invite him to the beach during the photoshoot.
b) *Optional* repeat 340 step at Friday or Saturday. Billy will be there this time.