My understanding is that India would require a deal that provides large numbers of visas to Indians wishing to go to the UK
No issues with that. I have worked in India several times I can vouch for their ability. A population of that size has to have some very capable people.
The US will require a lowering of food standards to allow their products be sold in the UK
No issues with that either. Worked in USA for 2 years and have visited USA many time on holiday. Their food has not made me ill. So all this nonsense about chlorinated chicken is just to scare people as EU does not want people to be offered cheaper alternatives as is exposes their cartel. Same with Australian beef being hormone treated. I currently live in Malaysia and a lot of food comes from Australia. Has it made me ill? Never.
Japan and South Korea are not major exporters of food.
Greenland exports a lot of fish products, but once out of the EU the UK will be able to source themselves
Mexico export fruit, vegtables and coffee
Ukraine exports mostly minerals and petroleum products
Turkey is more into apparel and textiles
Iceland exports fish products, but UK will be okay for such once fishing is returned to UK
South Africa export is mostly gold, diamonds, minerals, machinery, cars.