You must be a citizen to sponsor a parent.
A child (or anyone) must be at least 21 years old to file a sponsor petition except that there is no minimum age to file a petition for a spouse.
If the border agent believes a person is intending to stay here, they will not let them in until they have a green card. If a border or airport inspector believes that a marraige is planned, the person can be sent back immediately and barred from re-entry for 5 years.
A fiancee visa (K) is a non-immigrant visa. It is not a green card visa. A Non-immigrant visa does not have a preference category or a cut-off date since there is no limit to the number of K visas that can be issued. The Petitioner may be interviewed by the BCIS in the US then the K visa beneficiary is interviewed by the consul to see if he/she intends to marry the petitioner. The beneficiary also has to take the immigrant medical exam since they are expected to marry within 90 days of entry and then apply for a green card. It typically takes 6 to 8 months for a “K” visa to be issued.
A “K3”: visa allows the spouse of a US citizen to come to the US to wait for processing to be completed.
A fiancee visa takes about 6 months to get approved. Illegal entry can lead to deportation. If a US citizen helps a person enter illegally, the citizen can be charged with criminal violations. Consuls rarely expedite anything.
A. When a country reaches its annual limit, then a queue or waiting list is started. The date of the cases eligible to apply for a visa appears in the Visa Bulletin. If Visa Bulletin has separate columns for countries that reach their limit in some categories.
An immigrant visa can be issued only when the applicant’s priority date is earlier than the date shown in the current Visa Bulletin. It is the country of BIRTH (not citizenship) that is used for quotas. Exception: in a petition case with derivative benefits, a husband and wife can use each others country quota (and a child can use the quota of a parent’s country) when they travel to enter the US together. If a husband is India born and the wife is UK born, when they accompany each other to enter the US as immigrants, they can use the quota for India or UK, whichever is better. This is called “cross-chargeability”.