Advice needed for child living with parents with 7 yrs route

Hi all,
Could some one please advice on child living with the parents for 7 yrs route as one of my good friend who's living with their child for more than 7 yrs in the UK , according to home office link https://www.gov.uk/remain-in-uk-family/eligibility

they should be able to apply further leave to remain in the UK.

it would be best if some one can share more information on this route like would this be hard to get in to this visa category or how long would it take to get this visa etc.

thanks

Of interest - Freemovement article

https://www.freemovement.org.uk/can-chi ... residence/

Note:
"The Home Office approach to such cases is to say that where the parents have no separate right to remain in the UK under the Immigration Rules — which is in almost all cases — then it would almost always be reasonable for the child to accompany his or her parents abroad back to the country of nationality."

and

"The Home Office position in almost all cases seems to be that it would be reasonable for a child to accompany his or her parents abroad, so very few applications under this rule are currently succeeding."