Hi, will oil leach out of this hose into the gas when refilling tanks? should an lp filter be used? thanks

The OP has a valid question. Indeed look up YT "Mr Heater Hose" videos. They either use a filter or the new Mr Heater hose doesn't use any oil. Oil you say? Yes, some propane hoses have oil or related internal treatments for flexibility. This can slowly come out into the propane. Thus the Mr Heater oil filter trap. Note that most things won't care about any residual oil. But catalytic heater beds can slowly contaminate; same for propane lantern mantles. So to the OP? I don't know. To @tonys66ca the OP has a valid question.

Hi, Can this be used to attach a 1lb propane bottle to a standard 20lb propane regulator to my torch set up?

Don’t know what your torch setup looks like but if it attaches to a one pound bottle normally then yes it attach to your torch setup

Will it really refill a 1lb cylinder and if it doesn’t can the hose be returned for a full refund

Yes it really fills a one pound bottle, but you have to vent the bottle every once in awhile to allow pressure to lower so it can continue filling

Can I use this to refill a 5 lb tank if I use a small tank to large tank adapter?

I kind of doubt it. I use this to refill the small (1 lb?) Coleman type canisters. This works well with some tricks: Freeze the small Coleman type for a few hours before refilling. Turn the larger "BBQ" type tank upside down, attach the adapter hose and ideally fill the smaller canister at a lower level than the larger tank. Don't open the valve all the way just a bit and, if necessary, shake the small canister a bit and listen for the incoming propane. A properly full Coleman type canister weighs about 31 OZ. Not sure this helps all that much in your situation but FWIW.