how much time it takes for the nepalese people ? Is visa guaranteed after 10-12 years ?

Generally speaking, it currently takes about 12-13 years to immigrate through the F-4 category for siblings of US citizens. An immigrant visa is not assured at the end although the percentage of success is very high. A factor that could come into play is President Trump's proposal that the category be abolished completely. Also the visa applicant must be of good moral character and not have incurred a bar to coming to the US such as convictions, fraud or misrepresentation, terrorism, communism, or even not passing the public charge ground which is being made much tougher by the president. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.