Only if the referendum is on accepting the deal or going onto WTO rules, as the referendum on whether to leave or not has been decided on already.
Nope - what if people would actually prefer remaining to either 'real' brexit options of a deal or WTO. The original referendum was lopsided with a clear and know option on one side (remain) and a collective of theoretical brexits on the other - including many which were simply fantasy and others that are mutually incompatible.
No actual and deliverable brexit has been tested electorally against remaining. Once we have a deal then it should be tested against remaining. Only then can anyone justifiably claim there is a mandate for the actual brexit (not some hypothetical, undeliverable, cake and eat it brexit).
Why are you so scared - are you perhaps just a tad worried that we will end up with a pig's ear of a deal, clearly bad for Britain, and one that the electorate wouldn't prefer to the option of remaining.
If the brexiters are so confident of getting a great deal, why are they so worried about putting that deal to the electorate - surely they'd be completely confident of winning a second referendum against remaining.