Firstly since the property is registered now you can go ahead with the purchase the title of the property is clear.

Secondly if the construction was done with approval of panchayat no seperate approvals needed now.

No changes is required as at time of construction the property was under panchayat and the plans are approved by the panchayat.

You can take30 years title search to check whether title is clear and marketable 

2) if seller has original documents of title and property not subject to any encumbrance you can purchase the property 

Check whether property taxes bills are paid 

whether seller has original documents 

1. If the present owner of the property has purchases the land the basis of the notarised deed of transfer then bo valid titile has passed on him and hence he has no lawful right to sell as well

2. So you in the sale deed if you can manage to add the original owner of his legal heirs from whim your seller had bought this land on the basis of a notatised deed then only you will get valid title over this property.

3. Please note tat Mutation is mere proof possession and it does not create any title in the property on this basis.

Yes you can purchase the same but take noc and indemnity bond for the same 

1.  The Gram Panchayat was no legal jurisdiction to sanction Plans for any house construction, in its area.  This authority is vested ONLY with the Town Planning dept., or the Municipal dept.

2.  Payment of Municipal taxes or any other taxes will not regularize such properties, wherein the Municipal authorities derive rights to demolish or penalize or regularize the same.  Hence you will need to find such details with the local Municipal Office, about the legality of the building /house.  Do this using the services of a local Property lawyer.  Till then, wait before investing your money.

What do you meant by registered in 2018 ? Sale deed registered, if yes than you can purchase it, ask the seller to provide non encumbrance certificate. And no dues from Municipality, electricity etc.

First of all check all the relevant documents show it to expert local property lawyer. Take a legal search and title report from lawyer. Issue a public notice in daily local news paper . 

The property was originally purchased by someone by a notarised deed and not by a registered document.

Subsequently he constructed a house and got it registered, however there is no registered mother deed for this property.

Therefore it can be assumed that the original mother deed or title document is held by the previous owner as on date.

The municipal taxes or any other relevant papers cannot constitute the title to the property.

Have you obtained any legal opinion from a local advocate by producing all the relevant papers before him?

If not, do it immediately and proceed only when recommended.

There is no much difference in the property status, it was under village earlier and now within the limits of municipality, by that the value of the property might have increased.

You may approach a local advocate and obtain a legal opinion with proper recommendation before buying the property.

Yes you can go ahead with the purchase as the title is clear and approval of gram panchayat has been obtained before registration of property.

Also the owner is paying the taxes regularly then it is updated as personal property in revenue records.