Rulesman

Under the UK handicap system, solo rounds must be pre-declared and the player must be accompanied by an approved marker. As I understand it, under USGA system, there is no pre-declaration and the player simply has to be accompanied.

The significance is being in the UK as opposed to the US

When you said 'solo' I assumed you were on your own

Who will be your marker?

You must be. A standard cart path is usually over 4' wide, a driver is rarely over 4'

Not quite. You don't get to choose the spot, it must be placed as near as possible to the spot where it first struck a part of the course when re-dropped.

All here https://www.randa.org/en/rulesequipment/rules/rulesmodernisation

14-1a/6 Player Holds Club with Left Hand and Moves Ball by Striking Shaft with Other Hand Q.A player addresses his ball lying in high grass on a steep bank. His ball does not move, but the player believes it will move if he takes a backswing. Accordingly, the player holds the club with his left hand and strikes the shaft of the club with his right hand, thereby moving the ball. Is this permissible? A.No. The player pushed the ball, contrary to Rule 14-1.

Remember - it all changes in 2019. eg Flagstick may be left in hole when putting. 2 stroke/loss of hole penalties converted to 1 stroke. Ball hitting equipment. Double hits. Accidental movement of ball ................

The 'typo' isn't the problem. He didn't do what he is required to do. After completion of the round, the competitor should check his score for each hole

When would you not 'let it go' ? If he got two holes wrong?

17-4. Ball Resting Against Flagstick When a player's ball rests against the flagstick in the hole and the ball is not holed, the player or another person authorized by him may move or remove the flagstick, and if the ball falls into the hole, the player is deemed to have holed out with his last stroke; otherwise, the ball, if moved, must be placed on the lip of the hole, without penalty. 17-4/3 Ball Resting Against Flagstick Moves Away from Hole When Flagstick Removed by Opponent or Fellow-Competitor Q.A player's ball is resting against the flagstick. Without the player's authority, his opponent or a fellow-competitor removes the flagstick and the ball moves away from the hole. What is the ruling? A.In match play, the opponent incurs a penalty stroke and the ball must be replaced against the flagstick (Rule 18-3b). In stroke play, the ball must be replaced against the flagstick without penalty to anyone (Rule 18-4). In either form of play, the player may then move or remove the flagstick as prescribed in Rule 17-4.

It may not be worth getting anything for the time being. The Rules are all changing in 2019. But I reckon the USGA will have a brief guide out by then. But there is this https://www.usgapublications.com/products/a-quick-guide-to-the-rules-of-golf?variant=25702056198 It may be worth looking at the 2019 rules though, as you will have no preconceived ideas https://www.usgapublications.com/products/the-players-edition-of-the-rules-of-golf?variant=12581304270928

Has he got tartan feet?

No problem confirmed. But would you be allowed on the course wearing carpet slippers and no socks?