What will happen if Submission Limit is reached

Hi, will the jotform become unusable when it reaches 100 submissions, or if it can still be completed and we’ll still receive the emails submission, the forms just won’t be stored on the site?

I assume you are referring to the 100 submissions allowed per month for a free account. Forms are temporarily disabled/unusable if the monthly limit for any plan is reached. 

If you've reached your monthly limits, you can either wait for the limit which happens every 1st day of each month, or upgrade your to a higher plan to increase your monthly limits.