If you don't rotate them and end up with uneven wear (or if you replace just two), the tyres with the most tread should go on the back — there is less chance of pirouetting when slamming the brakes on in the wet. Obviously, your options are limited if you have different sizes front and back.
Punctures are very rare these days, I went for years without having one. Then, this year, I had two about six weeks apart. (Head torches are a great idea, I recommend that you carry one.) I would not want to be without a spare. If I take out my space-saver and a bit of black polystyrene, I can carry a full-size spare.
Even in relatively flat Essex, phoning the AA can involve walking a mile or two to somewhere with a mobile phone signal. I certainly wouldn't want to be in the hillier or more remote parts of the UK without a spare.
From the RAC website,
https://www.rac.co.uk/drive/news/rac-news/how-the-rac-universal-spare-wheel-fixes-no-spare-breakdowns/In 2018 our patrols dealt with almost 200,000 ‘puncture no spare’ breakdowns – an increase of 84% on 2012.
Julian F. G. W.