Existing leave of Tier 4 after applying Dependent visa

[Tier 4]

If Tier 4 migrant has 3 months existing leave left and intent to change his status out of country from Tier 4 (General) to Tier 4 dependent, can he come back to UK on his existing leave (in case of refusal) OR it would curtail automatically after applying another visa?

[geriatrix]

Any current leave is invalidated only if a new application for entry clearance or leave to remain is approved and has an issue date earlier than the expiry date of the current leave.

Whether the person may be able to (re)enter UK on the current leave, following an EC refusal, will depend on the person's circumstances (321A(1)).