Can you use guns, knives etc extra dice rolls when you are asked to test strength. Are these extra dice only used for combat situations or can you use them for events that require strength but are not necessarily a combat
thanks for any advice
It depends on the asset. If the asset says "Gain +1 strength in Combat Encounters" then you can only use it in Combat situations (specifically, combat with a monster token- text on cards describing a fight and asking you to test strength don't count!) If the asset says just "Gain +1 strength" you can use it whenever, regardless of what the asset is.
Most weapons will limit themselves to combat encounters, but the thing that defines the effect is the text, not the keywords.