Answer 1

This can be done using "exception handling," found in the section of the app "Exceptions and Files". Refer to that for more information. If you haven't yet reached it I wouldn't worry about it, but you could always look up more online!
Here's the revised code to create an exception to the ValueError (when the input is not an integer):

while True:
try:
x = int(input("Enter number: "))
while x <= 30:
print(x)
x = x + 1
if x >= 30:
print("Finished")
quit()

except(ValueError):
print('Error, not a valid number. Try again...')

I hope that helps! I know I changed around in the code though, lmk if you have questions. Good luck!

Answer 2

there is also isdigit which checks to see if something is a digit that can help.