ANW featured as a COBALT stock in the ASX by Small Caps, page-530

No, the ASX issues a a price/volume query to the company is there is abnormal/unexplained surges in price and volume. The company has a few hours (max one day) to respond. The ASX can't impose trading halts, trading halts are requested by the company. The ASX can impose a suspension, but they don't slap suspensions on companies just because of a price jump. They might if they are not satisfied with the response, but to give you a sense of how rare this is, see AUZ in November - they didn't cop a suspension despite the ASX's dissatisfaction with their response. https://hotcopper.com.au/threads/ann-response-to-asx-aware-letter.3809424/).

If the the company is unable to respond quickly to the ASX aware letter, the company can request a TH (if they believe they can sort it out within two days) or a voluntary suspension (if they believe it will take longer than two days to sort out).

You are on the right track though, guaranteed the ASX would have issued the letter so you can expect a ANW respond on Monday. There would have been one on Friday but the volume and SP action came in very late.

Read this: https://www.asx.com.au/documents/rules/gn16_trading_halts.pdf

Trading halts are easily the most mis-understood listing rules on HC. People either think they are used by the company when they have big news to release (good or bad) or they think they are a regulatory tool wielded by the ASX. Both are incorrect. It all comes back to continuous disclosure rules. If you have news, you must disclose it. If you're not in a position to disclose it, but the information you have is material, the company should request a trading halt to give them time to put the announcement together. Common examples are when a company is about to conduct a CR (one that doesn't require shareholder approval) or drilling results are known but key info that would be needed in the announcement (say one or two remaining drill hole assays) is not yet available.