10p is not a digit. A digit is an integer in the range 0-9.
Leaving that aside, you can make 31 sums from the 5 coins. If you allow 0 as a valid sum, the answer is 32.
Yuo can make only one combination of 30 digits using 30 digits.
Twelve of them.
24
2578 5287 5782 8572
Assuming each of the given digits can be used only once, the answer is 24. If not, the answer is infinity.
18 of them.
It is possible to create infinitely many numbers, of infinitely many different lengths, using the digits of the given number. Using each of the digits, and only once, there are 5! = 120 different permutations.
If you want 4-digit numbers, there are 24 of them.
Using only positive digits, and disregarding their order, 3 ways.
If you use them only once each, you can make 15 combinations. 1 with all four digits, 4 with 3 digits, 6 with 2 digits, and 4 with 1 digit. There is also a combination containing no digits making 16 = 24 combinations from 4 elements.
0
6 for 3-digits, 6 for 2-digits, 3 for 1-digits, and 15 for all of the combinations