1) For H1B, the offer made by Oracle was higher than the minimum wage guideline by DOL for those specific positions. You get a copy of the H1B petition submitted by Oracle and it includes all of this data.
2) Your salary is dependent on what you negotiated with your recruitment coordinator (Oracle will not change your figure once an offer has been sent to you). The recruitment coordinator makes an offer and you try as much as possible to counter. If you have prior work experience, you will most likely use your previous salary information as a basis for negotiation. I assume this figure you have quoted will form a basis for what Oracle will offer you. If you don't have prior work experience, then of course, they will make you an offer that they prefer.
3) Oracle pay increases are rare and typically small. This is why your starting salary is quite important because it basically forms the basis for your income for your years at Oracle