engine block mystery bolts? 2trfe (2005)

i understand the hole above the oil filter fitting is for a sensor but i cannot for the life of me find what goes in the circled ones. I though i read or heard somewhere at the start of my build that the biggest one is for a coolant drain plug but my yota dealer says its not. Any help?} Picture are appreciated, i have a crap tone extra bolts i may recognize.

 

Mine has a plug on the top one, then the left side is the coolant drain, and below the circled area is the oil pressure sensor

 

Looks like the big hole is just a plug, the one below it is the coolant drain. Not sure about the 2 holes by the freeze plug.

 

The top one above the freeze plug is not used and the one below is where the belt tensioner mounts to the side of the block

 

That almost looks like in was designed to mount something that needed access to the water jacket. That larger freeze plug and it's two threaded mounting holes on ether side looks allot like a mounting point for a block heater.