The most important duty of a state is its effective control over and responsible application of the monopoly on violence, delegated to it by its citizens, in the service of the protection of its citizens, and the protection of all people present within its territory.
All the other trappings of statehood — a currency, a post office, universal healthcare, the name of your state on a placard at the UN General Assembly, some transportation infrastructure of some sort, passports, some stamps you can apply to passports issued by other states, a national Olympic team and/or Eurovision Song Contest entry (as appropriate), a flag — are nice to have, but not really essential.
Article 121a Immigration Control
121(a)2 and 121(a)3 define the high-level framework for immigration control. For countries that do limit immigration, the arrangement here is not particularly controversial. “Limitation of social services” would be a dog-whistle to the right wing, were it not being shouted through a megaphone, and is predicated on the assumption1 that migrants come into the country for the welfare. But otherwise, so far, so good.
So. My first piece of advice to anyone seeking to cross their home country on muscle power alone: move someplace tiny with a complicated border. Like Switzerland.