You can get a US Entry Waiver for 1 year, 2 years or 5 years. Usually first time applicants get approved for 1 year, but you never know, so apply for 5. And yes, you do have to re-apply each time... keep in mind too that if you have a pardon, you will still need a US waiver.
6 months to 1 year
A waiver of WHAT ?
No.
up to 90 days (no extensions allowed)
The scholarship will take the form of a partial fee waiver.
You would need either an I- 212 waiver or I- 601 waiver. For serious crimes there is no waiver.
No, not for the Visa Waiver participant nations. It has to be done from outside the US.
First of all, the term "waiver" comes up in Immigration law more than once and, in more than one case the term is related to a visa. Most commonly, "visa waiver" and "waiver of inadmissibility." There is a difference between a visa waiver and a waiver of inadmissibility. A visa waiver applies when a qualifying alien comes to the United States without formally applying for a waiver at a US consulate.
Yes, but it requires a waiver.
This may not be possible at all. There is a penalty if you enter the US illegally. If there was ILLEGAL entry, then it would take a trip to the U.S. embassy/consulate in that person's native country and have a successful I-601 waiver. These are hard to win, but if it is approved, then it would be about 18+ months before the person can enter as a permanent residency. If the waiver is denied, then the person cannot enter the U.S. for 10 years- however, it is highly unlikely that such a person would be granted a visa in the future, making it a permanent ban.
U.S army
Yes but it requires the grant of a waiver.
The United Kingdom is a member of the Visa Waiver Program. This means you do not need to apply for a separate tourist visa to enter the United States. Entry on the Visa Waiver Program grants you up to 90 days' stay in the US. When you enter, you will receive a little white form called an I-90 and the officer will stamp it with how long you can stay. Be sure to check it carefully because there is no guarantee the officer will give you 90 days' stay.