A couple of questions regarding expert mode

I just came back to Terraria to continue my expert mode playthrough and seems like I have forgotten few things.

Before I decided to take a break, I was attempting brain of cthulhu and now it took me around 10 tries to get him down. Thing is, I'm kinda lost right now. Do I go for skeletron? or the jungle? In my normal game, I went for skeletron and the dungeon then for the underworld and hardmode, skipping jungle completely. -> This is my first question. What do I do next? My gear is: https://i.imgur.com/dxJgjXG.png Everything upgraded with Warding(got 40 defense) pretty sure skeletron would kill me as I had very hard time with the brain.

My second question would be: destroy demon altars or not? Been fishing for crates to help the transition from normal to hardmode so that monsters wont 1-hit me. I could farm tons of crates and just open them all at the start to avoid destroying altars and corrupting my world even more, but that would mean no mining at all and basically skipping the beginning of hardmode (Wouldn't that be kinda lame?! Skipping the content?)

Third and final question for now: https://imgur.com/It3wMOj what are those 'pots' it's obviously not a clay pot, but something different that you can use to plant the seeds in?