@minekpo1 ok, here's my point:
a) if you want to support every browser, you need to stick to the basics, as HTML is backwards compatible
b) it really depends on what you're targeting, you don't necessarily have to rewrite your website. But make sure it is accessible, that's what matters.
c) only by using old plain HTML stuff (i'll explain later)
d) my website isn't specifically designed for those browsers, it's more like trying to make it look nice on as many browsers as possible. That requires the use of both modern and obsolete stuff, in order to make things look nice, but still there are stuff that are hit-or-miss, like images. Personally i test my website mostly on Pale Moon (which is my main browser), but also on Links (both in graphical and text mode) and on Dillo. So far i haven't noticed any issues there. Maybe it's because of my setup in some cases.
e) Alt text is important, so yeah, long alt text doesn't look that nice. But the thing is that lots of people who use text browsers, probably don't care about the looks that much.
f) I know that <center> and tables are obsolete, but if you want to design around browsers that don't support CSS, you probably have to do it. That's why i use both CSS and these old stuff. Also, I don't like centering images with CSS, it's unnecessarily a pain in the ass.