He lacks the requisite experience for developing his skill.
I understand that "...ing" we use only in continuous tense. If I am right then under what rule we have used developing in the sentence above.
Your "rule" about tense only applies to verbs. In this case, the -ing word is a gerund (which is a noun). As such, it has no tense. "Developing" introduces a gerund (noun) phrase which serves as the prepositional object of "for".
Pope of the Dictionary.com Forum