You can only initially apply for a 3 month ' retirement' visa- they are then extended by 12 months at a time, assuming all requirements are in place. They are not new visas, just perpetual extentions on the original 3 months.
Much easier if you keep it going like this, precedent seems to be important.
This is just a guess, but doesn't it need to be a current account balance and not in investment accounts? The idea is you have this money to draw upon to support yourself (however you actually do it in reality)
you are obliged to inform the government of any change of address independently of anything to do with visas . Its part of your 90 reporting cycle, not visa application. I've just done it myself.