@Peregrina
You missed out referendums. An application to re-join without a referendum would be seen as an admission by the government it was not sure it's what people wanted.
As per the Miller law passed in 2017, the UK was not allowed to leave the EU without a vote by parliament on the deal. The same law will apply to a re-join and any proposed deal will have to be supported by a majority of MPs.
To save face, and avoid any admission that UK's departure was a disadvantage to the EU, the UK will be offered a deal that is substantially worse than that what UK had before. This will be used as an argument not to re-join. It would also serve Brussels purpose of discouraging other members from leaving.
Also, Article 49 requires all members to agree an application to join the EU. This will likely be the biggest hurdle as most members will want assurance they will be better off. For example, Spain may demand that Gibraltar is relinquished by the UK before agreeing to accept UK application.
This creates a conundrum for France and Germany in particular as it may seem like an admission that EU needed the UK. Weaker countries would not be bothered about France and Germany losing face as they are net takers and couldn't care less if it increased the amount they can take from the EU.