Is the brain sequence similar to reality or not?

I have not seen the movie so I have not seen the tools themselves. However operations which require cutting bone often require tools which might at first glance look like conventional power tools, such as drills. Tools designed for operations are designed to be very controllable in terms of speeds and the cutting implements themselves are made of high quality materials to prevent contamination, and can be autoclaved to be sterilized (using high pressure and temperature) but essentially they are not that far removed from hardware tools.

In terms of being awake during surgery. The main reason to anaesthetise a patient in an operation is to prevent the pain and stop any movement which would disturb the operation. The scalp itself has pain receptors but the brain has none, once the work has progressed into the brain itself no pain from that part would be felt, but with a local topical anaesthetic the scalp might not be too painful. One could imagine that you could be awake but not be in much discomfort in a brain operation.

I saw a video on the Discovery Channel where a Doctor was performing hip surgery. He used a DeWalt battery powered drill during the operation. I don't remember if it was wrapped in plastic or not, but I think the idea that a power tool is off limits simply because it's a power tool isn't right.

If the Doctor is doing something like screw a 4" medical bolt into your leg, then the standard equipment might not have the torque.

You can take a look at medial power tools at Alibaba.com to see what they look like. Some of the drills look a lot like regular drills you'd find in a store.

No, a Doctor would never use a circular saw in surgery, but they would use a reciprocating saw or a oscillating cutter. I'm sure there are medical grade versions of those.