Personal background
I'm currently in my thirties. I began my math path with self studying some of the university courses while in high school thanks to the guidance of a prolific mentor at the university ( he passed away a few years ago in a tragic accident). Then it continued a bit backwards and by the time when I entered university I started out with PhD and masters level courses in pure mathematics. Mainly because those were the interesting courses that kept my motivation high. I took the more mantatory courses towards the last years as "fillers".
I was in the process of starting out with my 4th year thesis in my third year of studies (older type of Master degree) when my PhD programe application that I had good letters of recommendations for got rejected. This rejection together with becoming a bit burned out and feeling a bit of general social abstinence from the solitary nature of my self studies led me to abandon pure maths. Instead I started to study applied maths. I got into finance/insurance without a thesis where I'm working ever since with mainly mathematical modeling.
Current situation
Maths has always been my passion. I generally feel motivated by my work but there's a longing for some more of an intellectual challenge. I opened some of my old books in Algebraic Geometry during the COVID-19 quarantine and noticed how much I actually remembered from back then. This lit my spark in a way I have not experienced with my otherwise mundane work. My motivation other than the pure interest I have in the subject is that I feel that not having a thesis is a failure that I want to remedy. It will also be useful for future work prospects I believe. I don't think I will become a researcher because I don't have the time and dexterity with two kids or the brain plasticity at this age. It's a long road after all.
I'm currently self studying algebraic geometry from the "bible" Hartshorne amongst other books. I have a past PhD course in algebraic geometry but since it was so long ago I'm attending a masters level course in the subject. I'm also thinking that completing it will help convince potential advisors that I'm serious and that I'm not just talking.
I have enough credits from my past studies for a masters in pure mathematics. The things I lack is a thesis. Two actually, one B.Sc which is a prerequisite for a M.Sc these days.
Questions
Given my perhaps a bit unorthodox experience with mathematics and the fact that I don't have any degree. How do I approach professors and ask them to take me on to write a B.Sc thesis? I feel like my age and long hiatus might put many of them off. Normally I would probably visit them in the office and talk, but these COVID-19 times when everyone's working from home that's not possible. I don't want "anyone" as a supervisor because I'm not doing this only for a degree but because I see it now as my hobby. So I want to write it about a subject that I will enjoy.
When I was in the process of thinking what I want and how I asked a few professors about supervising a M.Sc thesis (even though I don't have an actual B.Sc degree yet, I didn't know this was required) through mail. Everyone of them replied that they didn't have the time in the coming period but that I should ask professor X. Did I burn my bridges with them?
Taking a semester off from work for the B.Sc (I will take time off once I get to the M.Sc, however), is not an option and I do fine currently with studying on the side of my other obligations. I want to combine my work and writing the B.Sc thesis by planning to write most of it during the summer and some as I am on parental leave with my our newborn next year. This seems very specific and might put off many potential advisors. How do I touch on this subject in my contact?