1975 Aljo trailer...

How do i test everything from my house to make sure it all works? Electrical, range, heater, fridge etc.. The range, the fridge and the heater are gas, the rest electric

Make sure your refrigerator is level and turn on the propane and test the frig and see if the pilot stays on after you let up on the primer nob and turn it to max, then to desired number that isn't freezing stuff. Next day try it on electric.

Try the stove top and oven. Sometimes you have to bleed the lines aka let it run through a little so gas is there instead of air. See if the oven pilot stays on. Sometimes tapping the lines to with a wrench helps clear the lines.

Same with the heater. Make sure the pilot stays on after you let up on the primer nob and turn it to the desired number. Sometimes you have to do it several times as the gas flow blows out the pilot.. Again, tapping the lines too helps sometimes.

Using an extension cord to the house should be okay for what little runs on electricity but make sure the freezer compartment of the frig is level.

I have two early '70's trailers and they can keep you on your toes year to year with things plugging up. Gotta blow the heater out on one. Bees got in with it just sitting all summer..

Good luck.