Is it possible to achieve PPL on a recreational aircraft (RPC, sling)?... I suspect RPC aircraft will need to be VH registered...? As I saw some school advertise possibility of achieving CPL on a recreational aircraft....!

Yes, as long as the aircraft is on the VH register, then you're good to go. For a CPL flight test you'll need a TAS of at least 120 kts though, which is usually beyond what recreational aircraft are capable of.

... and a CSU?

Yep and as long as the book says it can crack 120...who gives a damn what it will actually do.

To qualify for CPL flight test, you need and aircraft with a cruising speed of 120KTS and a Manually Adjustable Pitch Control (MAPC).
There is NO RA aircraft that meets those specifications. Try Piper Archer III or Cessna 182RG.

Errr... no. Not correct sorry. There are plenty that fit that criteria. The fact that they aren’t VH is a different kettle of fish and a different conversation.

Oops... my typo... Archer should read Arrow.

I would look at CASR Part 61, section I (India) for requirement on VH.

I think you'll find there is no Archer that meets those specifications either

My mistake... I meant to type Arrow

What you'll find is the schools using RA-Aus aircraft for CPL operate in the following manner

RA-Aus aircraft used to achieve RPC + Nav Endorsement.
RPC+Nav is converted to RPL+Nav and flight review to activate.
Student completes Command building in RA or VH aircraft
VH registered complex (MPPC+120kts) aircraft used for around 30 hours of dual CPL training, and final flight test.

You don't even need MPPC. People do CPL's in DA42's and Cirrus that don't have a blue pitch lever. The DA42's don't even have a mix lever and still valid for CPL tests.