That's the contingency: Where is the separation of product? Apple isn't strictly a hardware company more than it's strictly a software company. If you consider the iPhone a unified inseparable product, then the ability to install other apps is a privilege
Sort of. Some printers have built the print head (with low MTBF) into the ink cartridge itself. You can refill once, but by the second time the output will be really bad.
Some printers ship with only partially-filled cartridges. This winds up being destructive on several fronts - users feel buying a whole new printer is cheaper than buying all the refill cartridges, not understanding that the new cartridges are different than what they had. This means the printer company is constantly selling new printers at a loss, with functional printer hardware thrown away to make space.
The print cartridges also usually sell with an XL-size option that appears cheaper overall. However, people who feel they should buy a new printer rather than cartridges are typically people who are at an ultra-low usage level (<10 pages per month). Even at the normal size, they are not going to make it through the ink before the cartridge starts to degrade with age.
HP rolled out a printer monitoring/ink subscription service which may solve these problems - assuming people feel it is financially sound to subscribe.
There may be other laws that would prohibit that, but they aren't anti-trust laws.