Couldn't you substitute a D12 with 2 D6? Just roll the first dice remember the number and then roll the second and if the roll is even add 6? Shouldn't that work?
What you described would work, but it's not usually what people mean when they say "2d6". 2d6, or any number of dice in an XdY format, means rolling X number of Y-sided dice and adding the results together. The specific case of 2d6 vs 1d12 comes up a lot in D&D because there are some common weapons that use those two values for their damage rolls
Yes you can. First result = 0, second = 1 to 9. You either roll two different color dice, or you roll one and then the other, but one is used for the tens place and the other for the ones.
Back in my day we didn’t have d10s! Our d20s were marked 0-9 twice and we inked ‘em in different colours, black for 1-10 and red for 11-20, reading the 0 as 10 or 20, respectively. And we LIKED it!