Bloodborne's post-release patches add several balance changes and decrease load times. However, I'd like to learn to speedrun the game, and the fastest possible speedrun route requires two glitches that were fixed in later patches. So if I apply the patch for its benefits, can I remove it at will for the sake of speedrunning?
The only way to remove a patch is to delete the entire game then do a fresh install from the disk.
You will then have to either manually stop the patches from downloading, possibly every time you start your PS4, or disconnect from the internet completely.
I would make a back up of your save files, uninstalling the game should not delete your saves but better to be safe than sorry.
Also your current save files may not be compatible with the un-patched version of the game, so you may have to install the current patch to use your existing saves. This is the case with certain games but I am not sure if it applies to Bloodborne.
I doubt this would be possible with a digital copy of the game as it will always download the fully patched version.