Firstly, download a downgrader from Dark_AleX's site,
here. Since the 2.50/2.60 downgrader requires GTA:LCS, you may need to upgrade then use the appropriate downgrader.
Download the 3.40 oe-a easy installer,
here; It will give you firmware 3.40 oe-a, which enables you to use homebrew and illegal materials + the latest Sony firmware features.
From there, search for all the homebrew you could possibly imagine
here.