Mr. HeaterPropane One Pound Tank Refill Adapter

When using a re-filled 1 lb bottle with the Portable Buddy Heater, do I need to use the Mr. Heater Fuel Filter between the bottle and the heater?

Is it possible to refill a coleman 1lb disposable propane bottle with this adapter?

how to tell when if is full ?

Various sources say to connect to a 'full' 20 lb tank to refill the empty disposable bottles. I understand a full tank might have better pressure, so how many bottles can I expect to refill from a 'freshly refilled 20 lb tank' OR 'is it imperative that I use a full tank to do the refills'?