Welcome to the forum.
#1. No, there is no limit for the number of apps you publish on the appstore.
But there are limits on how you upload:
AFAIK, there is a limit for the number of apps uploaded in a certain period of time. Here they say 20 (but no official number): https://medium.com/@tranhuuphuc20051995/the-reality-behind-app-store-connect-has-a-limit-of-n-binary-uploads-per-day-90a85ed072fd
forbidden to spam the Appstore with multiple variations of the same app (you risk account cancellation if you do so). Reaching the daily limit is hard and could lead to spam suspicion.
More here: https://stackoverflow.com/questions/26462287/number-of-app-limit-on-appstore
#2. What do you mean ? If you publish a new release, of course you can. Which means it has a new build and version numbers (incremented).
If that answers your questions, don't forget to close the thread by marking the answer as correct. Otherwise, explain your question more in depth.