Yes. It is actually easier to sponsor using the Ancestry visa than if you are a British citizen as there is no minimum income threshold.

No. You only need to prove that you are able to work and genuinely intend to seek employment.

Descent from the grandparent to the parent, and from the parent to the applicant, is permitted through adoption. However the grandparent must have been born in the UK originally. You cannot trace to a grandparent who was only adopted in the UK. The adoption must be by a process recognised as valid for the purposes of UK law.

No. Descent can include through the father of an illegitimate child where he is proved to be the father.

An Ancestry visa results in 5 years leave to remain. At the end of 5 years, the applicant is eligible for settlement if they still meet the requirements of the rule. There are minimum residence requirements.

Yes. Typically this is only necessary if the person did not acquire indefinite leave to remain or British citizenship, or subsequently lost that status. If any new visa is used any previous leave is automatically cancelled.

The Immigration Bill 1971, clause 2(1)(c), originally said that a Commonwealth citizen would have the right of abode in the UK if they were the child or grandchild of a person having Citizenship of the UK and Colonies (or before 1949, the status of a British subject) by birth in the UK or Islands. During the passage of the Bill, the right of abode was restricted to those whose parents (not grandparents) were born in the UK. The Ancestry visa has in effect compensated people who lost out during this amendment by providing that they can still apply to come to the UK to work.