In slider crank mechanism, secondary forces fluctuate at

Bernoulli's principle

Venturimeter works on the basis of Bernoulli's principle.
The Bernoulli's equation states that For a perfect incompressible liquid, flowing in a continuous stream, the total energy of a particle remains the same, while the particle moves from one point to another.
The Bernoulli's equation is applied to venturimeter, orifice meter and pitot tube.

1 and 2

In thermodynamics, a process in Quasi-static process and Reversible process undergoes a succession of equilibrium states.

2 and 3

In thermodynamics
Work is path dependent function
Work is area under the curve in a PV diagram

2 and 3

Heat and Work are not completely interchangeable forms of energy
Work can be converted completely into heat