is it legal to file damage claim with two insurers for same item ?

Nope, not legal. Not in any jurisdiction.

All insurance policy contracts have a clause written into them that says (basically) "this policy will not cover anything that another policy will cover". You won't find an insurance contract anywhere in the civilized world that doesn't have that condition.

Sometimes it happens where one loss is covered by two policies, and no fraud is involved in any way. Maybe a tree falls on a car you rented, and it's covered by both your primary auto policy and your credit card agreement as an added bonus. In cases like that, both insurance companies will deny coverage at first (because no policy covers something another policy will cover) and then settle the matter of who covers how much in court. It happens all the time.

If it's a case of double-dipping, where fraud is involved, both insurance companies will just tell the insured (the customer) to go to hell and cancel the contract, then report them to the police. That happens all the time too.

Titled property such as a home or car, would show the name of the insurance company providing coverage. That would raise a flag with the 2nd insurance company. Besides, I would think the premiums on two policies would not be cost effective. Competing insurance companies do have a communication network among themselves. But you can have multiple life insurance policies on an individual. Some policies share coverage such as primary health insurance followed by supplemental health insurance.

You can only claim from more than one insurance policy if the terms of the policies are such that it is recognised that they each only cover part of the total liability. You are only likely to get policies like this when you insure a VERY expensive item, or event. In that case insurance companies are happy to share the risk.

Yes. However you cannot collect twice on one claim. The insurers prorate their payments based on the total amount of coverage. It is illegal to collect twice.

Yes you can, however they will try work out on each other like one pay half and other pay another half. Or you can pick only one who has better coverages.

You can if you think you want to, but you can only collect once.

If both insurers covered the item, why not?