As I said in my first comment: run solo on the beach, charm her and defeat her.
As for events, if you browse galery and see 3 locked on the first page and 6 on the next one - those are Friday party random events, I suggest unlocking all the other first and then using cheat code to get them all as grinding it is very tedious and RNG based
To reach the lab you have to follow yosuke's quest (guy with orange headphones that you met at the party)
By accessories I mean cat ears, thigh highs, virgin killer sweater, choker - not consumables like you mentioned books ingredients or special night consumables