Some File Upload field Questions

Hello, a presale question

#1 Is there could be file size limit & Number of files for the file upload?
#2 Where is all files go, a folder in wp-content/uploads/ ?
#3 If so, is there an option to clear all files from the Files Uploaded Folder?
#4 Is there a condition where to determine the field show/hide, like the field display only if the payment method is selected to A.

Thanks