Can you specify what kind of "spend" do you mean?
Do you mean spending BTC for shopping or other payment methods?
Well, the utility of BTC is exactly important, moreover, it will increase the value and also the trust of bitcoin itself. However, it doesn't mean that if BTC is not spent on it, the value will significantly decrease.
No.
As long as there is still supply and demand of the BTC in the crypto market, the BTC will still have value and also volume. There will be still many people who concern in BTC and take profits from it. If many people are investing, it is also not complicated. It is good enough. except if there are more people who are selling BTC than buying, this will make ethe price down.