Ask an Immigration Solicitor. Get an Answer ASAP.
3. The application is made online here https://www.gov.uk/apply-uk-visa. The form is in the following format at this link https://www.gov.uk/government/publications/application-for-visa-family-settlement-or-reunion-form-appendix-1-vaf4a. Only use this form VAF if you cannot apply online. Be aware that your mother will have to show that you will be able to support her and that she will not be a burden upon the state. She will have to pay the healthcare surcharge and else buy private healthcare insurance for the first five years she is in the UK. https://www.gov.uk/healthcare-immigration-application/overview. This will set out how much she has to pay. Here is a link to the government website which provides you a general overview https://www.gov.uk/join-family-in-uk/overview. Look at the sections which apply to an adult dependent relative. Best of luck.