Nope... it's the weekend and coming out of the lock-down, people tend to get out from behind the monitor :)
In addition the question was pretty broad and requires someone to spend a good deal of time to answer. I'll take a stab at a couple of the basics. There's a lot of info here as well, search is your friend.
First, it's never too late to start riding. My father rode well into his 70's. No, he wasn't launching big triples, or jumping at all for that matter, but he always had a blast.
Next, what kind of riding are you wanting to do? MX Tracks, Trails, Desert? You mentioned sand. The general idea is to stay on the throttle and keep the front end light. You mentioned foot out/down/forward. It 1) get's more weight on the front tire, which aids traction 2) if you start to tip, you can dab it to kept from falling over. Never have been a fan of #2, can't be hard on the knees, but there it is.
Riding principles are the same regardless of age, so just about any source of instruction will be good. Gary Semics has been around for ever and has a old, but good set of videos/dvd's a LOT of us old guys learned the basics from him.
Motocross Training & Techniques DVDs - GSMXS.com There are many sources out there with all the info you can handle.
Just be prepared to take it easy starting out, dirt is a lot different than street (duh), be prepared for some get-off's, it's just part of the game. Get yourself geared-up properly. Spend the $$ for a good set of knee braces, boots and obviously the best helmet you can afford. This isnt an inexpensive hobby, but hospitals cost a lot more.
If you've got specific questions, let us know. Welcome to DRN!