Suppose we have public key: $$n= 1015, e= 3$$ and private key: $$d=  635, p=  35, q=  29, \phi(n)=  952$$For $m = 100$, we have $$c = m^e ~mod~n = 100^3 mod~1015 = 225.$$To decipher this, let us take $$c^d~mod~n$$ which is $$225^{635}~mod~1015$$ which equals $$680$$ But $680 \neq 100$ so this means that RSA incorrectly decrypted it right? Why does this happen?
Issues in RSA setup
cryptography;encryption;modular arithmetic
Your public key is not a legal RSA public key.  In RSA, $n$ must be a product of two primes, but 35 is not a prime.  Therefore, things don't work right: for instance, you got the wrong value of $\phi(n)$.