Phone -> Voicemail -> Greeting in the upper right corner. You can play the current audio and record a new one.

Visual voicemail is about showing the text of messages that you receive.

As you mentioned, setting an alarm through Sleep Schedule is what I’d suggest. I use the “Sunny” tone and it starts quiet and grows to full volume after about 5-10 seconds.

I doubt it’s harmful. I believe the phone sets the charging rate, up to what the wall charger can supply. Beyond that, power is power.

I use these Anker GaN chargers for many of my Apple devices, as well as a bigger one for a laptop. No complaints or unusual battery wear.

No, it’s whack. Turn off the alert.

Watch estimates my VO2 max at 25. Other estimates put it at 45-46 based on my min/max heart rate, which aligns more with my actual fitness. I don’t record Apple workouts very often though, I often use it as a Peloton HR Monitor.

Try this:

(max heart rate on an all-out, gassed workout / resting heart rate) * 15.3

Disclaimer: Not a doctor nor a watch.

Try pressing the crown and button together for at least 10 seconds to see if it’ll hard reset.

Beyond that - if the battery is no longer holding its charge, then it’s $100 for an Apple Store replacement, in the US at least. For that much money, it’s probably better to save towards a newer & faster watch and maybe get a small trade-in on yours. I know that’s not a good answer when you’re broke, but Apple watches just aren’t easy to repair.