Your body regulates it’s own pH. You won’t be changing your pH with food, otherwise everything would just make us sick all the time
The lemon juice in containers, I guess it depends on brand. Reallemon is pretty good, tastes the same as normal lemon juice. Most brands are shit tho
I think the worst it’ll do is give you heart burn honestly. Your stomach acid is Wayyy more acidic than lemons. Same with the alkaline water. Doesn’t do anything but sound cool the acid in your stomach will bring it to level within minutes.
Lemon in your water does literally nothing apart from make the water taste different. I’m sure you’ve put a few drops of lemon on fish before and it didn’t change your life like lemon water people claim.