Is this correct?

[Prosperity]

Hi all

Thanks and sorry for the upcoming long post.
my mum was granted ILR back in 2003 due to the fact that she had a dependent (ME) that was born in the UK. However, my citizenship was meant to be processed straight after but it wasn't done. we were informed the lawyer made an impromptu visit back home and never returned. I lost a few family members, mum became extremely ill. Fast forward, am now actively trying to sort out my passport and was informed by a lawyer that at the time my mum was given ILR I was also given one as I am her dependent and she received the ILR because of me. Is this correct? (First question) Also my main option is to register as a British citizen, it says it in the document provided from home office to my mum, however, due to the fact that I am now over 18 (which would have been a very easy process if under 18 and still kick myself at the fact that it wasn't done but I had a very difficult childhood) well I now have to provide evidence of life evidence, I was informed by the lawyer that this doesn't necessarily have to start from 0-10 but can be from 7-17, 9-19, 10-20...As long as one of the first 10 years of your life is included and continuously provide proof for 10years from that (2nd question). Thank you very much in advance.