I'm curios about this if any one could answer it :)
My first recommendation is to research a bit on what others have done. David Windestal (formerly Flite Test) flew an FPV glider to 100,000 ft and there are some interesting insights you can gain from that. LINK, and DETAILED ARTICLE
As you can see from his video, communication was a big big issue. I'm not a digital signal processing (DSP) engineer, but to accomplish your mission I recommend that either you become an expert on DSP, or find someone who is. That's going to be one of your biggest challenges.
Side note: If I was going to pick an off-the-shelf transmitter/receiver for this project, I would pick an OpenLRS Tx/Rx, which are open source transmitters and receivers. Open source is awesome!
Some things to note:
- There is not a lot of air at 100,000 ft, so that micro drone will have a tough time maintaining altitude - and more likely will fall spectacularly back to earth, unless it has some gigantic propellers. Do these calculations or some ground experiments to determine whether it can maintain altitude.
- To maintain attitude control (your second question, I think) you must have some kind of attitude control system. As is said above, propellers will most likely not work for this. Compressed air and a series of valves and nozzles is the cheapest bet. That's what the SpaceShipOne guys in Mojave did for their flight to... (see "Vehicle Description")
Anyway, best of luck to you, and do keep us in the loop and updated - that's what the community is here for!