"There is one big gap in this family and it is my Grandmother. She was Clara Ann Robinson born I believe in April 1881 at Elkesley. I have a copy of her birth certificate and it is dated Second April 1883
Mother is Sarah Robinson General Work. No father is listed When registered Twelfth May 1883."
You say you believe she was born April 1881 but have her birth cert saying 1883.
Kate Robinson was registered Jun 1881 at E Retford 7b/13, there is also a Arthur Butt Robinson with the same registration details.
The 1881 census was on the 3rd April, so if one of the girls birthdays was on 2nd April she should be only be a day old on the census. The census image looks like 2 weeks. I could not find a death for this Clara , so a bit of a tangle there with names, Could Sarah have called her Clara initially and then decide she liked Kate better? She certainly baptised her as Kate in the May 1881.
I think it unlikely she left 2 years to register a birth as there was a consequence to doing that.
Fanny's baptism date does not tie with her census age either -according to that she was born 1886 and baptised 1898, so she would have been around 12 at her baptism.