Ask an Immigration Solicitor. Get an Answer ASAP.
First of all you cannot switch from a visitors visa to a Tier 2 visa while in the UK as a visitor. When you do get a job that is willing to sponsor you, your application should include your son as a dependant.
Your 20 years old son is not a minor under UK immigration law and therefore cannot be your dependant.
He is an adult and would be expected to apply to come to the UK like every other adults above the age of 18.
What mental health issue? He is dyslexic? Many adults in the UK are dyslexic and still go about their normal lives. It isnt enough to present dyslexia as a reason for your adult son to join you as a dependant under UK immigration law.
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