Question

Which will be more stable carbocation upon heterolysis of `"C"-"Cl"` bond?

Answer 1

Consider the consequence of the heterolysis you describe for each, in turn,

`(1)`

This would be stabilized by resonance,

`(2)`

The cyclic ether would be acting as an electron donating group, stabilizing the positive charge.

`(3)`

This is stabilized by hyperconjugation to the highest degree (`3°`).

`(4)`

This is a primary carbocation: a very unstable molecule.

As a result of this qualitative analysis, `(1)` and `(3)` are very close in stability, but I would wager `(1)` is slightly more stable. Resonance is a very powerful effect.