Is it possible to restrict the access to our JotForm once it has been embedded in our website?

2. Does jotform provide a service where we restrict access (on our website) to the form, have the user create an account, with payment and save their progress and finish later?

The only way to protect a form would be asking for a word and check if it is correct to show the fields in your form, you will need to first add the Text Box field where you will ask for this secret word to enter to the form:

Once it has been added then you will need to set up a condition to show the fields in your form if the correct word has been entered: 

You would also use a Form Collapse tool to hide multiple fields at the same time, so you avoid handling multiple fields in the same condition. 

Once you have added it, set the field to be opened and hidden: 

You will also need to only select the collapse tool in the condition instead of all the fields. 

Here is also the link to my sample form, please enter "abc123" to get all the fields in it: https://form.jotform.com/62525153048957 

Hope this helps.