Computational feasible to reverse MD5SUM?
Actually, to the best of our knowledge, it's computationally infeasible.

By the terminology what we use when we discuss cryptographical hash functions, you're not asking for a hash collision (which is "find two different messages that hash to the same value"), but instead you're asking for a hash preimage (which is "for this hash value, find a message that hashes to it").

While MD5 is known to be woefully inadequate when it comes to resistance to hash collisions, there is no known way to find hash preimages that is faster than brute force (that is, hash different message until you stumble across one that happens to hash to the target value).  This brute force approach with MD5 will take $O(2^{128})$ expected operations, and so it is computationally impractical.