You’ve confused two separate things in the Brexit process.
It’s worth remembering what’s actually going on. The UK informed the EU of it’s intention to leave in 2 years (March 2019) which means all treaties are gone. Zero cooperation. For the EU, the UK becomes legally equivalent to North Korea unless there’s a deal. People say it’d never happen, they’d agree something but of course that something is a deal! That’s the default position - North Korea.
At the minute, the negotiations are on the Withdrawal Agreement. Which basically boils down to the UK gets two years pretend EU membership, the right to negotiate but not enact trade deals with the rest of the world, no formal political representation on EU bodies, pays up what it said it would to the EU budget, guarantees the rights of EU national in the UK and of course the backstop to prevent a hard border between Ireland and Northern Ireland after the two year grace period ends.
All that’s pretty much agreed except the backstop.
There are occasionally noises about other awkward loose ends in the Withdrawal Agreement like geographic trade marks (champagne can only come from Champagne in France, Parma ham from Parma etc). They’re considered small enough and I could see a symbolic row over something inconsequential before the Withdrawal Agreement is finalised.
All the tedious developments at the minute are reformulations of how the backstop would work but who knows what will make the final text. There’s no point speculating.
If a final text is agreed, the UK will have to pass it through their parliament but also the EU must pass it through the European Parliament (that powerless body that does nothing!) and all the Member States have a veto.
Then we’re into the future relationship. Assuming the Withdrawal Agreement holds, that means ~no changes until 2021.
However, with the end of the Withdrawal Agreement’s two year transition period, the UK becomes to the EU legally equivalent to North Korea. Unless a long term trade deal sorts that. (Back to square one).
That’s where Chequers comes in. It’s the UK’s pitch on what the future trade will look like. It tries to avoid the backstop being required by harmonising the UK to the EU for physical goods only. There’s other fluff around computer tracking goods for customs but that’s purely for show. Interestingly rather than reference EU law or state full harmonisation Chequers uses a convoluted locution on how the goods would be the same in the UK and EU. Suggesting they were leaving space for stroke pulling to gain an advantage.
In any case, the EU rejected Chequers on sight. So who knows what the 2021 trade deal will look like. But for the UK, it is always going to be a trade off between adherence to EU law and access to the EU single market. Low adherence = low access.
Generally trade agreements worth having take decades to sort and the consensus is that the two year transition period is wholly inadequate. A problem for a different day.