4. What is the difference between the different TLDs?
They can signify different things for example, .com for commerce/commercial, .org for organization, .edu for education, .gov for government, .online indicating an online presence not tied to a specific location.
However, even if they were originally intended for a specific purpose, many of these now are generic and can be used for any purpose. Country extensions like .ae .uk .ca .us and .jp indicate the site is specific to that country
'.com' is the most popular TLD, meaning that your audience might expect that your domain name will end with .com. However, being very popular also means that it will be harder to find an available domain name with it compared to other TLDs.
There are many TLDs to choose from, you should consider your audience when selecting one. For example, if you think your audience will trust you more with a '.com' then find an available name with '.com'. If '.online' is suitable for your website and your audience will find it appropiate, then use it.
Country specific TLDs and a few others like .gov have restrictions on who can use them based on if you are located in the specified country or if you are a government agency. However, for most other TLDs, there are no specific rules governing their use. You can choose a TLD that best suits your interest or business purpose. According to Google, your TLD choice and whether is contains a keyword or not (e.g '.store') will “not give any advantage or disadvantage in search.” Ultimately, the only difference that a TLD will make is if its percieved as trustworthy by users. And even newer TLDs are becoming more popular and therefore more trustworthy.
Also, the different TLDs usually have different prices.