Questions on part time H1b

I have some questions about part time H1b.

Situation:
A part time H1b was approved with permission to work for 10 hours per week, $20/hour. Now, if the employer is willing to let the beneficiary work (with the same job duty) 15 hours per week with a raise to $25/hour,

Questions:
1. Does the employer need to file a new part time H1b petition for the beneficiary? Or just an amendment (or something else)?
2. If the total working hours per week is not changed, but a raise (to $30/hour) is given, still need a new part time H1b petition?

I thank you for your time to answer my questions.