As the others have opted out, I will step in. Please note that you have actually asked at least five separate questions in your original post...
1. "Afterwards, one party discovers that the other concealed assets. What are the courses of reparation,"
This answer is for situations where the property was acquired during the marriage and NOT by inheritance or any other way that keeps it from becoming marital property.
Generally, two options: A. A motion to modify the divorce decree to adjust the property settlement; or
B. A new lawsuit for fraud (less favorable, more expensive, etc.) IF all elements can be proven, in general, a misrepresentation of a material fact (nature and extent of marital assets, the victim's reasonable reliance on that misrepresentation, and damages from the lie and relying on it. For PA's exact language, google "Pennsylvania fraud elements".
Note that fraudulently concealing *marital* assets during property settlement negotiations is technically a fraud on the court, and warrants a modification even without the usually-required "material change in circumstances."
2. Afterwards, one party discovers that the other concealed assets. What are the courses of reparation,
Yes, and it depends on what course of action is chosen.
For a fraud lawsuit, PA controls:
"§ 5524. Two year limitation.
The following actions and proceedings must be commenced within two years:
(7) Any other action or proceeding to recover damages for injury to person or property which is founded on negligent, intentional, or otherwise tortious conduct or any other action or proceeding sounding in trespass, including deceit or fraud, except an action or proceeding subject to another limitation specified in this subchapter.”
For modifying a divorce decree, it appears to be four years:
§ 5525. Four year limitation.
(a) General rule.--Except as provided for in subsection (b), the following actions and proceedings must be commenced within four years:
[. . .]
(5) An action upon a judgment or decree of any court of the United States or of any state.
Unfortunately, it would take an excessive amount of time to check the PA Rules of Civil Procedure for more guidance on this. Rule 56 might control that.
3. Also are there any categories of assets that would not fit under the usual "common property" PA laws, including for example--real estate, retirement income and assets, bank accounts regardless of where they are held, inheritances before the marriage, cars planes and boats, investments ?
No, there is no limitation on the types of classes of property that can become marital property. Note that inheritances AFTER the marriage are also separate property. Gifts to one spouse are separate property. The main other after-acquired property that is always separate property is proceeds from personal injury causes of action.
ANY separate property can be transmuted to marital property by something showing a clear intent to share it with the spouse--like depositing money into a joint bank account.
4. Suppose one spouse has separate income from investments and retirement funds acquired before marriage, but then let's the other spouse pay nearly all living expenses and acquires new real estate property, planes, new investment funds etc. by feeding their assets into these new acquisitions. Are the new acquisitions by the spouse during the marriage subject to disclosure and division at the time of divorce ?
How a couple chooses to pay for living expenses is their business and does not alter the marital nature of earnings during the marriage. If it was purchased with marital money (earnings), it is presumed to be marital property until proven otherwise. AND all property must be disclosed.
5. Also, "what is the definition of newly acquired assets" during the marriage.
That is not the right question. The question is HOW the property was acquired during the marriage. See above. Gifts and inheritances are not marital property. For example, in most states, lottery winnings are marital property--even in a fairly famous case 20-30? years ago where the winnings came in literally the day before the judge finally bothered to sign the decree. They had been waiting for WEEKS. But the rules are the rules.
6. Would any new purchase of real estate, cars, planes, property improvements, salaries or consulting fees, stock, shares or partnerships or other interests in corporations qualify, and if not what are the exceptions?
It all needs to be disclosed. Period.