If Honda uses its company name to cover such different products as its automobiles, lawn mowers, and motorcycles, this branding strategy is known as?

When a company expands its brand into new markets (new product category targeting different audience/territories), it is called brand extension. They will be capitalizing on the established brand reputation to drive customers to buy the new product. This is the case here for Honda. They are selling different products that serve different markets using the same brand name. If you trust Honda cars you are very likely to trust their motorbikes. So, the case here for Honda is  "brand extension".

Multi-brand is when the same company tries to sell similar products labeled under different brand names. Example, if I sell Kawazaki motorbikes and Yamaha motorbikes (which are similar in specs and already competing in the market) in my showroom. This is not the case here. Honda's products are sold under the same brand name and are not competing within each other.

Line extension is when the company uses an existing brand name for a new item in a product category. Example, if Honda makes a new model within the motorbike category targeted for food delivery fleets. This is not the case here.

New brand is when you create a completely new brand name for your company or one of the products/lines. Again this is not the case here. The same brand is being used across all product lines.

However, a more challenging case is "Acura". Acura is a sub brand of Honda that offers the higher-end automobiles. It does not compete with the main line of Honda automobiles (because it is in a different price category) so it is not a "multi-brand strategy". We can argue it is a "brand extension" but I rule that out because it is not a new product category; Honda already has an automobile category. We might argue it is a "new brand" (which it is indeed with a different name, logo, and a private website), however, it is still listed on Honda's website on the main menu as one of Honda's product lines. So, it is a sub-brand that is kept closely related to its parent brand. Is it a line extension? most likely because it is a new product that extends an existing category (the automobile category)...

Thank you for the invitation.

My answer is (4).

Thank you for invitation. My answer is 4. Brand extension strategy.

Number 3 Multi-brand, I guess.

I think that the answer is multi brand strategy. Honda is a parent name and all the other segments are its SBUs i.e. different brands therefore multi brand strategy.

Referring to your example "Honda" I would choose number 4; brand extension strategy in the form of franchise extension 

Multi brand strategy because they are moving towards other brands..and making other strategy for every segment of products.