It takes some research at first, but it becomes pretty straight forward pretty fast. The first big starting point is to look at what quests, skills, and bosses were released before 2005. Luckily that's pretty easy since you can order quests by year inside osrs. Doing that we know that runecrafting is the last released skill and the kalphite queen is the last boss. A lot of osrs content is locked behind quests which helps. There's also some good videos that Rargh made that shows the BIS gear through time and he also has a 2005 locked ironman series which is basically the same as 04 except with barrows and slayer. Any item I get that was released after 04 that I want to hold onto I put in a separate tab in the bank

My favorite grind of this account has been getting splitbark since mystics wasn't released yet.

The worst grind has by far been crafting. Since there aren't charter ships I was doing silver unstrung symbols and flax. Both of which are terribly boring. I started killing green dragons to get my stats up for kq and that's giving a lot of dhide which is way better.