A Court can find that a prescriptive easement has been created after five or more years of continuous, open, notorious, use of the property over which the easement runs. The use must be "hostile" to the interest of the owner of the property. If the use is with the permission of the owner, prescriptive rights cannot be aquired.
This answer does not constitue legal advice, nor does it creat an attorney/client relationship. If you are seeking legal advice upon which you intend to rely, you should hire competent cousel familiar with this area of the law in your locale.
Attorney Boss is correct. In order to establish an easement by prescription it must be shown that the easement was used continuously for a period of five years and possessed in a manner that was open, notorious, and clearly visible to the owner of the burdened land and hostile and adverse to the owner. The burden would be on the party asserting an easement to prove all of the elements necessary to establish it. This is not easy and would require an action to quiet title. Most of these cases, in my experience, are resolved by way of an agreement between the parties whereby the property rights as to the disputed property are established under the agreement, and formalized in recordable documents.
As to your second question, I would need more information.
The prior responses are correct. In answer to your question about whether you have the right to use the easement assuming you have used it for 5 years, yes you do. Although a court judgment declaring you have the right to use the easement would convulsively establish such use, the whole basis of a prescriptive easement is that you have used the property in a manner hostile to the legal owner of the property. So you have a right to continue that use. Sometimes people decide to file suit to establish their right, notwithstanding this, because they want certainty or they want to sell the property some day with the right already declared and not in doubt, and so they file suit. Your last question about rights in government land is not clear and requires further information.