Good advice above. My $0.02:
I agree that 71B is a great yeast for meads, especially with fruit, berries in particular. I prefer D47 for traditional meads, cyberspace, and other meads that come off as white wine like.
A lot of folks are having good luck with not ageing a year or more. I would trust their advice but if you are making wine strength meads I recommend longer if you can stand it.
Don’t ferment any higher than low 70s, remembering that the fermentation will take the temp about eight degrees higher than ambient temp, so a room in the mid sixties is the highest you want. Higher temps will create fuselage alcohols, making them taste “hot” and causing headaches. It’s the worst.
Agreed that it’s important to only heat honey enough to mix. Simply mix with hot water as you make the mead.
I rarely backsweeten. It’s a matter of preference. I find just about every commercial mead cloyingly sweet and much prefer the sweetness and mouthfeel of a mead that is comparable to a dry wine.
When adding yeast nutrient degas first to avoid eruptions. It’s best to ferment in a bucket with plenty of head space.
I recommend doing a mixed berry mead with 71b and a traditional mead with d47 for your first attempts.