Versions.asmx is supposed to work with files/documents not list items

to work with list item versions you should use Lists.asmx web service. however, it only provides method to retrieve versions but not to restore.

anyway, I don't think it's a good approach to manipulate versions just because item was not not approved.

at first, workflow itself, neither workflow task action do not do item's version update on its own (regardless of whether task is approved or not). versions are only update if you do any changes/updates to the item within workflow by purpose. so you moreless do not have what to restore.

at second, if you restored old(er) version you might lost some important information needed to restart workflow in case of troubles (eg. some intermediate steps/approvals) that would let you to restart workflow from step step where it failed.

I would suggest to maintain own approval status information within the list.

, did Marian's reply help you. Please let us know.

Hi Marian,

 I got a clear view about versions now. Thanks to you.

I have a situation where,

There are two lists Final and Temp with same data. Users can only modify Temp items and that item will be sent for approval. If item is approved, the respective/same item in Final list should be updated to this approved version. If rejected, this tem (in Temp list) should be updated to approved version in Final List (previous version).

I tried this but while updating I have to update the entire item not only the changed values.

Suggest me if there is any other way in achieving this.

Thanks!

so this has nothing to do with item's versions.

you just need to copy actual item version form one list to the other in one case and vice versa in the other.

if the lists are within the same site you even need not to use web serivices, you can use update item or update multiple items actions.