I live at high altitude where we have cold winters outdoors (under -5F, -25C minimums) but it stays sunny all year. I've lived with attached greenhouses for many years and they do a great job at heating the house and growing winter leafy veg and perennials that aren't quite hardy outdoors. We do get below freezing in the greenhouse some nights, probably low 20sF or -5C, though I'm not exactly sure.

I'd love to grow some of my own citrus. I've heard that Meyer lemons are naturally dwarfed, hardy to some degrees of frost. My questions are:

1) Would a Meyer lemon do well in a greenhouse with a 9 or 10 foot ceiling, and through Jan would have below-freezing (but windless) nights and sometimes very warm sunny days?

2) Would you recommend any other citrus for this purpose? I've also thought of figs. Any others?

3) Do citrus require or prefer a pollinating partner or can i plant just one?

Thanks!