Is It Possible For a Data Structure to Have Constant Time Access/Insertion/Deletion?
How do we get lower bounds?

As D.W. noted, lower bounds are hard. But that doesn't mean that no progress can be made. To get a lower bound, it is required (well, not strictly, but you won't get very far without one) that you make a (possible restrictive) model of all algorithms or data-structures that can solve your problem. 

For example, the $\Omega(n\log n)$ lower bound for sorting holds only for the restrictive 'comparison based sorting' algorithms. (this is why counting sort can 'beat' this time in some cases: it isn't comparison based)

Lower bounds for data structures

For the case of data-structures, the cell-probe model seems a good place to start. This model is similar to the more common RAM-model, but can be useful for lower bounds as it 'only counts' the number of accesses to stored data (i.e. the number of 'probes' to a cell).

For example, in the paper by Yao that introduces this model, lower bounds are calculated for the data structure supporting INSERT, DELETE and MEMBER (test for membership) queries. I think that a similar technique could work for your data-structure as well. 

Do note that the paper by Yao is a bit outdated. I mostly mentioned it because the problem it considered is relatively simple and similar to yours. More modern techniques are covered in the dissertation of Kasper Green Larsen.