It depends. Some numbers in area code 530 are local to you, but others are toll.
No, area code 850 is a regular geographic area code for the Florida panhandle, including Tallahassee and Pensacola. It is not toll-free unless you are within the local calling area.
Area code 855 in North America (USA, Canada, etc.) is toll-free numbers.
Walnut Creek, California, is in area code 925. All calls within area code 925 (local or toll) can be dialed with just the 7-digit local number, or optionally 1 + 925 + number. All calls to other area codes (local or toll) must be dialed as 1 + area code + number.
Area code 712 is an ordinary geographic area code for roughly the western third of Iowa, including Sioux City and Council Bluffs. If an area code 712 number is non-toll for you, that is because it is within your local calling area.
toll-free telephone numbers in the North American Numbering Plan. Area code 877 (Russia), Republic of Adygea.
It depends where in the USA or Canada you are located. In a few places, mostly rural areas, you can still dial a local call to an adjacent area code with just the 7-digit number. However, in more and more cases, you must dial either the area code plus the 7-digit number or 1 + AC + 7d, depending on whether or not your area has "toll alerting." (Toll alerting means that you must always dial "one plus" on all toll calls.) For example, in San Francisco, a toll call to San Rafael (long-distance, but within the same area code) can be dialed with just 7 digits, but a local call to Oakland (local, but in a different area code) must be dialed with 1+AC+7d. If you are using a cell phone, you may or may not be able to dial local calls in the area code where you are currently physically located as just 7 digits; local rules vary from place to place. However, to prevent confusion, it is best to enter all numbers on your cell phone with the area code.
Area code 866 is toll-free numbers within North America (USA, Canada, etc.). It is unlikely that a correctional institution would offer a toll-free number.
No, in North America (USA, Canada, etc.), area code 866 just means it's a toll-free number. There are certainly some scams with toll-free numbers, but the vast majority of toll-free numbers are legitimate. The toll-free codes in North America are 800, 888, 877, 866, 855, and 844, with 833 and 822 reserved for future toll-free use.
No, there are toll calls within Idaho. To dial a toll call within Idaho, you must dial 1-208 followed by the 7-digit local number, even though you are also in area code 208.
855 is for toll free numbers - it's not an area codes, and not assigned to a specific region.
There is not a good correlation between area codes and local calling areas in the United States. In some places, there are local calls to adjacent or nearby area codes. At the same time, a number in the same area code may be a toll call. Texas has something called "toll alerting." That means that if a number is a local call, you can dial it from a landline without dialing "one plus." If you are prompted to hang up and dial 1 to complete your call, then that is going to be considered a long distance call. The situation for the Dallas/Ft. Worth metropolitan area is complicated by the use of "Metro" numbers, which have a wider local calling area than non-Metro numbers in the same city. For example, a Ft. Worth Metro number is local to or from all of Dallas, but an ordinary Ft. Worth number to an ordinary Dallas number is a toll call. Most calls within area code 817 and overlay area code 682 are local calls. Some numbers in Dallas (214/972/469) and other nearby codes (254, 940, and 903/430) might also be local. Anything beyond that is definitely toll. The easiest way to find out if a number in North Texas is local or toll is to try dialing it on a regular landline with just the area code and number (e.g., 682-555-0123 instead of 1-682-555-0123). If the call goes through, it's local.