The last plumber suggested glue-ing (caulking) the toilet to the floor without any bolts. Is that the best solution for this ? Attaching the photo. The old flange does not gap to fit in the screws / bolts. My experience level is 1/10 :)
I would get a repair flange (screws to the old one) then fire your plumber because he should know how to install this 10$ repair kit. Added there are compression flanges closer to 40$ that will also work but I would choose the <10$ option.