Gas types

[Gatsby]

Hi,
I have seen talk about conversion kits for connecting to a house supply and have some questions.
Is LPG a gas bottle, Natural Gas a house supply (bayonet - sydney street connection) & what is a house supply from bottles (ie in the country)?

I assume a gas BBQ is designed for a bottle so what is the impact of connecting to a house (yes I know a new fitting and changing the jets)

What happens if the conversion is only half done - ie fitting changed to natural gas but jets not changed or other way?
I am assuming this is bad but how bad? Like low heat, too much heat, explosions, total devistation, extinction level event?

BTW I am only curious about this am not doing it - well other than my parents are having a gas stove (ilve) put in in the country on big mother gas bottles. (But it came with a conversion kit)

Ta

[food&fish]

To put a bottled gas appliance on nat gas you have to enlarge the jets if you dont you only get 1/2 or less heat
if you put a nat gas appliance on bottle gas you are likley to get a flair up