you haven't done any of this things and you certainly haven't answered the original question
Merits the same answer to Jason118 which was look at the other posts on other threads. In your case you have commented many times to my posts and vice versa.
That an answer to your question is not what you wanted to hear does not mean the question was not answered.
No deal was not the original objective, but seems to be the most likely based on the insistence by EU that the WA must remain. The WA in my view does not come close to respecting the 2016 referendum.
The legal advice given by the attorney general, Cox, stated that UK could be locked into the EU forever based on the wording that does not oblige the EU to accept any of the proposals made by UK with respect to the Irish border.
For UK to pay £39 billion to leave the EU, but to end up remaining in the EU forever is the worst deal imaginable. Hence why MPs voted against it, including those who voted remain.
Upside of a no deal are;
Proves that government delivered their promise to leave the EU. This restores confidence in government taking into account the number of times Uk government has made manifesto promises for the purpose of being elected only to ignore once they have been elected.
Potential instant savings of £39 billion. That goes a long way.
Free to trade directly with other countries without the need for EU approval. The world becomes open. Remember EU is 15% of world trade only.
Europe GDP growth is nowhere near that of the developing economies which are 85% of the World economy.
UK growth as an individual country exceeds the overall growth of the EU. Reason is that it subsides the other 18 EU members who do not pay into the EU, but take money from the EU.
No further subscriptions payable to the EU which saves UK 9 Billion per year.
Downsides
This is subjective as no other EU member has left the EU before so there is no hindsight to compare with. However, here is a try:
Free trade access with EU is lost overnight until new deals are made. Chaotic transition WTO very likely
Effect on GFA not clear and GFA may fall by the wayside. Hostilities that GFA was intended to eliminate may reappear
Not paying the exit bill may discourage other countries from trade deals
Many other examples could be added for sure