Is there any experienced runner here who can answer my queries, me being a new baby runner?

1. i run/ jog in the amul garden, which has a concrete path with red sand on it. I use puma rider rollin sneakers or puma basketball high ankle shoes and can run 2km without stopping until latic acid in my calves stops me.

After those 2km, which is approx 10 to 12 laps of the garden, i feel a little uncomfort in my left knee. should i wear anything to protect my knee from the jerk? upgrade shoes?

2. which jacket to buy which has ample chained pockets to store keys, buds, and mobile while running? currently using a m&s good move winter jacket, which i won't be able to continue wearing in the coming summers

3. after 1 km, from where to breathe? like i get lots of salaiva in my mouth during running, which i sallow and dont spit. should i spit? will it hamper my water levels while running? also, breathe via nose or mouth?

4. i tend to run more if i do stretching before running. which stretches are recommended to do before running?

thank you.