Supply to Boiler and pressure reducing valve question

Referencing the attached photo from the Installation Manual for the TT 100 solo, I have a question about the pressure reducing valve. It shows (unless I'm reading it wrong) the pressure relief valve looped around a ball valve. When the ball valve is closed, the water would be supplied at a reduced pressure by the reducing valve which is OK. My question is since I've never seen an installation like this:

1) Is the reason for the ball valve so that you can fill up the system quickly without going through the reducing valve?

2) Is the ball valve necessary?

Thanks,

You don't need the bypass valve. The prv has a quick fill feature built in.

valve

1. YEs. 2. Only if you want to be able to fill and flush rapidly. 3. I usually pipe the bypass around the reducing valve, but that is just a personal preference and has nothing to do with how it works. 4. Not all fill valves have the internal bypass/quick fill feature

Thanks guys!!!