This camera uses the older mercury cell. You can substitute with a zinc-air battery. Although they have shorter life, the battery voltage is close enough to the specs for the original mercury cell that your exposures should be accurate.
This offers a sort of program mode only. You cannot change aperture or shutter speeds manually. I think the only way to intentionally use a larger aperture would be through the use of neutral density filters.
It's a nice enough compact camera. I think Rollei used a bit too much plastic in their Singapore produced cameras.
On a brighter note, unlike most of its Japanese contemporaries, there are no foam seals, which by now have hardened or turned to goo. So you just have to make sure the rangefinder is accurate, and you're good to go.
I owned one of these in 1979 for about 10 minutes. It broke shortly after I left the store. I returned and got a refund.
Last year, I found one in excellent condition at a thrift shop for $7.95. This one is functioning as it should.
I notice that it doesn't have true aperture blades. Rather, it has two L-shaped blades that move closer to each other. That means the shape of the aperture is either a diamond or a tiny square (at its smallest setting).
Perhaps I'll load mine and see what it can do.
As far as I know, this was the first and only Rollei-branded 35mm rangefinder (true rangefinder, not zone focus) until it marketed the rebadged Bessa-R2 as the Rollei 35 RF in 2002/2003.