Is autistic child able to grow into math genius?

Yes. If the teachers have a structured curiculum with the ability to be firm. Many austistic kids are "visual" learnerss. Avoiding long verbal instructions is diffucult. Reading with phonics. Autism is not an intellectual deficit-in fact nonverbal intelligence can be quite high.
Yes but..... Depends on the severity of the autism. Very severely disabled children will have trouble expressing their skill.
Some. It is crucial for parents of autism spectrum children to seek out the unique and creative ways their children express themselves. At the same time, it is very important not to burden oneself and one's child with expectations that may not be fulfilled. All children (and adults) have natural inclinations and flourish best when those inclinations are seen, acknowledged and nurtured.