I'll help you with subscribing to QuickBooks and setting up your company name, @sokookwok-gmail-.
There shouldn't be any error when using the & symbol or character as part of your company name in QuickBooks Online. Since you're getting an error trying to set up your file, I recommend doing the steps using a private window. In most cases, unusual behavior or issues with QuickBooks happens due to the stocked cache of the regular browser you're using.
To access a private browser, you can use either of these shortcuts:
Google Chrome: Ctrl + Shift + N
Safari 11 or newer: ⌘ + Shift + N
Mozilla Firefox: Ctrl + Shift + P
Microsoft Edge: Ctrl + Shift + P
If it works fine, go back to your original browser and clear its cache to start fresh. Moreover, you can sign up or subscribe to QuickBooks using another supported and up-to-date browser to narrow down the result.
After setting up your account, you're now ready to start using QuickBooks. As your guide, you can check out the topics from our help articles. Here's the link: Help articles, video tutorials, and more.
If you have any other questions about QuickBooks, let me know by adding a comment below. I'm more than happy to help. Have a good one!
As an additional note, if you have to open a new QBO account, make sure to click the Buy button to get the discounted price for up to 3 months. If you purchase from the Trial account, you have to pay the regular rate.