Questions regarding ecommerce on squarespace

I want to start a small online store on your website, business annual plan looks good to me, but I have a few questions. If I take the annual plan can I cancel after some time and stop paying in case it doesn't fit me? Also, is there any way to allow payment with credit cards on my website without Stripe since it's not available in my country? If I use Flat Rate, how does that really work, if someone pays for a product do I just ship it to the address they've entered?