Q.mirabilis
If I plant seeds from my 4 o’clocks, will they eventually turn into tubers and how long will that take?
Thank you.

Four o'clocks reseed themselves liberally, so if you want to gather seeds and plant them, that should work. The tubers develop over the course of a summer, to help the plants through the winter. Here are a couple of articles that could give you some food for thought: https://www.gardeningknowhow.com/ornamental/flowers/four-oclocks/four-oclock-plants.htm
https://www.gardeningknowhow.com/edible/vegetables/vgen/preseeding-vegetables.htm