Careful, gauravsoni--in this context, swimming is a noun (gerund), not a verb. It describes an activity, not an action. It's the difference between "Cooking good food is not always easy" (Cooking=noun) and "He is cooking dinner" (cooking=verb).
The word "like" only compares nouns (unless we're using the verb form--"I like to cook."). "As" has many uses, as the guide suggests, and one of them is a prepositional form. So the answer to your original question, mydreammba, is "Yes." Both "like" and "as" can precede a noun phrase, depending on what we're trying to say:
As entry-level employees, Kelly and Hank are poorly paid and have little job security. (The word "as" indicates that Kelly and Henry are entry-level employees, and in this position/role, they are poorly paid and have little job security.)
Like entry-level employees, Kelly and Hank are poorly paid and have little job security. (The word "like" indicates that Kelly and Hank are similar to entry-level employees in terms of pay and job security, but they are not actually entry-level. Perhaps they have plenty of experience in very bad jobs!)
I hope this helps!
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