I'm not sure I can answer all your questions, but I definitely just wanted to say Hi, & Welcome!!
I think if you're starting on a journey to take better care of your hair then you've definitely come to the right place.
The big tips I personally used when my hair was long was to treat it like antique lace. The hair at the very ends is the oldest, the longer your hair is, the older that hair at the end is going to be.
Little or no heat. Long term use can be so damaging.
A lot of people recommend natural coloring over box coloring/bleaching. I used henna for YEARS and loved it. The red was very nice and never faded like a box color.
Detangle gently. Try to prevent breakage. I used only hair ties with no metal, or scrunchies or alligator clips when I put my hair up.
Wind and sun can be damaging too, so try to protect your hair when possible.
The oil thing.....It doesn't have to be coconut oil. I used extra virgin olive oil and only oiled the length. I feel confident in saying brand doesn't matter, but some people may prefer one brand over another....I think it's just whatever works for you or gives you the best results.
There are tons more tips....I think one of the forums is just for tips. This question might get more answers there than here....
But Welcome again!!