There are many circumstances/ incidents which may persuade the Court to upheld a claim of constructive dismissal. For example: sudden demotion, no work given, pay cut, no bonus/increment despite good work performance etc. As such, it is based on case to case basis. In my opinion, based on the facts given, it is my opinion that it may suffice to support your claim for constructive dismissal provided the said incidents/ decisions were not supported by any valid reason on the Company's part.
Yes, if u want to claim CD u have to resign immediately and any delay may affect the strength of your case as to claim CD u have to show to the court that the victimisation/ harassment were unbearable which you could not tolerate any much longer. Hence, the 24hours resignation.
Should the Industrial Court dismissed your claim for CD, the Company may claim from you the notice period. However from my legal experience, this has never happen for reason unknown (maybe the company had enough).
PLEASE TAKE NOTE, to claim for CD you need to properly draft two (2) letters to the Company with 3-7 days grace period between each letters. Failing which, your claim may be dismissed by the Industrial Court due to procedural error/ premature claim.
Hope this sufficiently clarify your query and u may email me should u need any further clarification.